HUMAN FACTORS REQUIREMENTS FOR REAL-TIME MOTORIST INFORMATION DISPLAYS

VOL, 5 BIBLIOGRAPHY AND SELECTED ANNOTATIONS: AUDIO SYSTEMS

John M. Mounce

@]

-CO"'NR"AlJ r. DUDEK FILE, C~OPY

R\:o\ld.._

[f@~®lffi from the Texas A&M

RESEARCH FOUNDATION College Station, Texas

Texa~ Transportation Institute Texas A&M University

College Sta ti on, Texas 77843

Prepared For

I

Federal Highway Administration Offices of Research and Development

Contract No. DOT-11-8505

February 1978

T•chnical Report Documentation Page

1. Report No. 2. Government Accenion No. 3. Recipient's Cotalog No.

FHWA-RD-78-9 i---------------'-""-- ---------------+~=----.,~---····--·---·-4. Title and Subtitle S. Report Date

HUMAN FACTORS REQUIREMENTS FOR REAL-TIME.MOTORIST February 1978 INFORMATION DISPLAYS 6.Pe~forrning Organization Code

Vol. 5 Bibliography and Selected Annotations: Audio ......,,,Sy_s_t_e.._m .... s~--· -------------------17. Performing Organization Report No.

7. Author's)

John M. Mounce 9, PorforMlng Or9aniaotian NOMe and Addren

Texas Transportation Institute Texas A&M University College Station, Texas 77843

·~-------------12. $ponaoring Agency NOMe and Addreu : U. S. Department of Transportation Federal Highway Administration Office of Research, Traffic Systems Division Washington, D.C. 20590 15. SuppleMentary Notes

FHWA Contract Manager · Principal Investigator · : Co-Princioal Investiaator: 16. Abstract

Truman M. Mast (HRS-31) Conrad L. Dudek R. Dille H11rhi nac:"n

10. Worlc Unit No. (TRAIS)

11. Contract or Gront No.

DOT-FH-11-8505 13. Type of Report ond _Period Covered

14. Sponsoring Agency Code

This report provides a review of past studies concerned with motorist informa­tion presentation using audio and mixed mode (visual and audio} signing techniques. The first part of the report presents a bibliography {through 1976} sub-divided into the following topic areas:

A. Real-Time Motorist Infonnation By Audio Systems· ·· B. Highway Radio Systems C. Speech, Hearing, and Co11111unication Techniques D. Audio Information: Presentation Rates, Length, Context, Format, Style E. Masking, Loudness, and Audio Intelligibility The latter part of the report contains selected annotations of directly relevant

studies involving audio and mixed mode information presentation.

17. Key Words Real-Time Motorist Information,

Audio Communication, Highway Radio System Audio Information Presentation, Audio In'.'" telligibility, Traffic Management, Traffit Diversion, Freeway Operations

18, Distribution StateMent

, No restrictions. This document is availa ble to the public through the National Technical Information Service, Springfiel,~ Virginia 22151

19. Socvrtty c1 ... 1f. (of thie rapart) 20. Security ClaHlf. (of thl s pogo) 21· Na. of PagH 22. Price

Unclassified Unclassified

Fon11 DOT F 1700.7 <•-72> Reproduction of form and completed page is authorized

· ..

PREFACE

This document is part of a seventeen-volume report entitled, Human Factors Re uirements For Real-Time Motorist Information Dis la s. Titles of a

FHWA-RD Volume Number

1 78-5 2 78-6

3 78-7 4 78-8 5 78-9 6 78-10 7 78-11 8 78-12 9 78-13

10 78-14

11 78-15

12 78-16

13 78-17 14 78-18 15 78-19 16 78-20 17 78-21

Title

Design Guide State of the Art: Messages and Displays in Freeway Corri­dors Sumnary of Systems in the United States Bibliography and Selected Annotations: Visual Systems Bibliography and Selected Annotations: Audio Systems Questionnaire Survey of Motorist Route Selection Criteria Analysis of Driver Requirements for Intercity Trips Analysis of Driver Requirements for Intracity Trips A Study of Physical Design Requirements for Motorist Infor­mation Matrix Signs Human Factors Evaluation of Traffic State Descriptor Variables Human Factors Evaluation of Route Diversion and Guidance Variables Supplement to Traffic State Descriptors and Route Diver­sion and Guidance Studies Human Factors Evaluation of Audio and Mixed Modal Variables Point Diversion for Special Events Field Studies Freeway Incident Management Field Studies Feasibility of Audio Signing Techniques Driver Response to Diversionary Information

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ACKNOWLEDGEMENTS

Special acknowledgement is made to Dr. Truman Mast, FHWA Contract Manager, for his invaluable counsel, advice, and guidance throughout this project. Dr. Mast worked closely with the research staff and was always available to share ideas and offer constructive cr1tique, adding more depth and dimension to this research project. His associates, particularly Jim Ballas and Joe Peters, are.recognized for their technical consultation and constructive criticism. Dr. John Eicher provided FHWA administrative support on this project. Acknowledgement is also made to Lawrence D. Powers, Lyle Saxton, and Samuel Tignor, who together with Truman Mast and John Eicher, developed the real-time motorist information display research program.

The author also wishes to expFess his appreciation to Dr. Conrad L. Dudek, the Project Principal Investigator, for his advice, guidance, and review of the report.

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. INTRODUCTION

The firstpart of the report is an initial listing of references identi­fied by the re~earch staff as possibly having some information and data rele­vant to the project research objectives concerned with audio and mixed mode signing. T.he list of references· is divided into the following classifications.

A. Real".' Time Motorists Information by Audio Conmunication B. Highway Radio Systems C. Speech, Hearing, and Communication Techniques D. Audio Information: Presentation Rates, Length, Context,

Format, Style E. Masking, Loudness, and Audio Intelligibility

The latter section of this report contains annotations of selected refer­ences. It is anticipated that additional references may be identified and annotated as the project needs dictate.

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BIBLIOGRAPHY .

A. Real-Time Motorist Information by Audio Communication

1. Quinn, C. E. New Voice System Alerts Drivers. Traffic Engineering, July 1959. ·

2. Hanysz, E.1 A., Stevens, J.E. and Meduvsky, A. Communication System

for Highway Traffic Control. Electronics, October 1960.

3. Morrison, H. M., Welch, A. F., and Hanysz, E. A. Automatic Highway and Driver Aid Developments. Presented at SAE National Automobile Week, Detroit, Michigan, March 1960. ·

4. Olsen, P. L. Road-Driver C01nmunications--1980, Proceedings,_ Insti­tute of Traffic Engineers, 1962.

5. Hanysz, E. A., et al. DAIR - A new Concept in Highway Communications System. Presented at IEEE VTG Conf., Detroit, Michigan, December 1971. '

6. Weinberg, M. I., Deley, N, J. and Schneeberger, R. F. Surveillance Methods and Ways of Communicating with Drivers. NCHRP Report 28, 1966.

7. Fowler, P. A New Look at Traffic Broadcasts. Auto Club News Pictorial, Automobile Club of Southern California, October 1967.

8. Dudek, C. L. and Jones, H. G. Real-Time Driver Information Needs for Urban Freeways. Texas Transportation Institute, Research Report 139-4, July 1970.

9. Sielman, P. F. Progress Report on the F1F1 Highway ColTVllunications System. Presented at IEEE VTG Conf., Detroit, Michigan, December 1971.

10. Case, H. W., Hulbert, S. F. and Beers, J. research Development of Changeable Messages for Freeway Traffic Com:,rol: Fin~l Report August 1971. ITTE, School of Engineering and Applied Science, UCLA.

11. Mccasland, W. R. Freeway Control and Information Systems. Texas Transportation Institute Research Report 139-13F, January 1972.

12. Dudek, C. L. and Carvell, J. D., Jr. Feasibility Investigation of Audio Modes for Real-Time Motorist Information in Urban Freeway Corri do rs. Da 11 as Freeway Corridor Study Report RF 953-8., April 1973.

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13. _ Huchingson, R, D. and Dudek, C. L\ Development of a Dial -.In Telephone System Based on Urban Freeway Motorists Opinions, Paper presented at the 54th Annual Meeting of Transportation Research Board, January 1975, Transportation Research Record, 1975.

14. Guide to Highway Corrmunications Systems Technology and Design, Report FHWA-RD-75~101, Federal Highway Administration, Traffic Systems Division, January 1975.

15. Gatling, F. P. Auditory Message Studies for Route Diversion. Federal Highway Administratian, July 1975.

16. Gatling, F. P. The Effect of Auditory and Visual Presentation of Navigational Messages on Message Retention. Federal Highway Admini­stration, June.1976.

17. Carvell, J. D. and Hatcher, D. R. Evaluation of a Dial-In Traffic Information System·. Report RF 953-25A, .July 1976.

18. Ristenbatt, M. P. A Comprehensive Motorist-Vehicle Communication System, (Undated).

19. Gordon, D. G., Gatling, F. P. and Harris, R. D. Auditory Communi­cation of Highway Information. Draft Report, lraffic Systems Division Office of Research, FHWA, (Undated).

20. Halstead, W. S. Roadside Radio in Theory and Practice. American Association of State Highway Officials, {Undated}.

21. Technical Considerations Regarding the Implementation of a Low Power Roadside Transmitting System at Broadcast Frequencies. Federal Highway Administration, {Undated). .

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B. Highway Radio Systems

1. Halstead, W. S. Electronic Communications on Highways. American Association of State Highway Officials: Committee Proceedings, p.p. 150-153' 1957.

2. Keller, J. E. The FCC andRadio Control of Traffic Control Devices. Traffic Engineering, May l."95~,

3. Covault, D. 0. and Bowes, R. \~. A Study of the Feasibility of Using Roadside Radio Communications for Traffic Control and Driver Infor­mation. Annual Report No. 1, Engineering Experiment Station, Ge·orgia Institute of Technology, February 1964, Highway Research Record 49, pp. 89-106, 1964.

4. Covault, D. 0., Dervish, T. and Kanen, A. C. Study of the Feasi­bility of Using Roadside Radio Cominunications for Traffic Control and Driver Information: Report No. 2, Highway Research Record 202, pp. 32-66, 1967.

5. Bauer, H. J., Quinn,~. E. and Malo, A. F. Response to a CB Radio Driver Aid Network. Highway Research Record No. 279, 1969.

6. Salterly, G. T., Jr. and Basu, S. Analysis of Citizens Band Radio Communication System as a Motorist Aid. Wayne State University, June 1970.

7. A Survey and Analysis of Citizens Radio Service. Advanced Technol­ogy Systems, Inc., April 23, 1971.

8. Dudek, C. L. and Cummings, D. Application of Commercial Radio to Freeway Communications - A Study of Driver Attitudes. Texas Trans­portation Institute Research Report 139-3, 1971.

9. Dudek, C. L., Friebele, J. D. and Lautzenheiser, R. C. Evaluation of Corrmercial Radio for Real-Time Driver Communication on Urban Freeways. Highway Research·Record 358, 1971.

10. Wolman, W. W. Letter to Members and Participants at the 1972 Mid­Year Meetfog of the HRB Communications Committee, Dated June 8, 1972.

11. Chiarmonte, R. M. and Kr§er, H. B. Measurin~~ the Effectiveness of a Volunteer Emergency-Monitoring System in tt1e Citizens Radio Service. Highway Risearch Record No. 402, 1972.

12. Stephany, S. J. Comments to a paper by Chiaramonte, R. M. and Kreer, H. B. Measuring the Effectiveness of a Volunteer Emergency-Monitoring System in the Citizens Radio Service. Highway Research Record No. 402, 1972.

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13. Quinn, C. E. A Hi~hway Gommunication System for the Motorist: The Case for Two-Way R~.dio," Highway Research Record No. 402, 1972.

14. Lavigne, R. L. Motorists' Radio System for Emergency Needs and Advisory Communications. Progress Report for Project 1-5, June 1973.

15. Campbell, R. Roadside Radio Smooths Traffic Flow. Popular Science, Volume 202, Apri 1 , 1973. .

16. Trabold, W. G. and Reese, G. H. Performance of .Volunteer Mbnitors Using Citizens Band Radio for a Highway Conununications Service. Transportation Research Record No. 495, 1974.

17. Anderson, R. A. and Robertson, R. G. Study and Development of Highway Advisory Irformati on Radio. · Atlantic Research Corporation. Research Report No. FHWA-RD-74-73, December 1974.

18. Lampert, S., Hulbert, S., and Jenkins, A. Restricted Range Radio Information Systems Evaluation Study. Institute of Safety and Systems Management, USC. Prepared for Los Angeles Department of Airports, Los Angeles, California, April 1974.

19. Hanysz, E. A. Highway Alert Radio. Research Laboratory Brochure, General Motors Corporation, Warren, Michigan, (Undated).

20. Hy-Com Highway Communicator. General Motors Corporation, Delco Radio Division, Kokomo, Indiana, Eng. Dept. Rep., (Undated}.

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c. Speech, Hearing, and Communicatfoli Techniques

1. Crandall, I. B. The Sounds of Speech.· ·Bell systems Techr'lital Journal, Vol. 4, pp. 586-626, 1925~i .

2. Baget, R. Human Speech. Harcourt, Brace., New York, 1930.

3. Shower, E. G. and Biddulph, R. Differential .. p;.tch Sensitivity of the Ear. Journal ·of the Acoustieal Sotiety·of·Anlerica, Vol. 3, p. 275, 1931. .

4. Stevens, S. S. and Davis, H. Hearing, Its Psychology and Physiology. John Wiley and Sons, New Yotk, 1938.

5. Potter, R. H., Dopp, G. A. and ~reen, H. C. Visible Speech. Van Nostrand, New York, 1947. ··

6. Beranek, L. L. The. Design of Speech Communication Systems. Proceed­ings of.the Institute of Radio.Engineering, Vol. 35, pp. 880-890, 1947.

7. Fletcher, H. Speech and Hearing in Conmunication. D. Van Nostrand Company, Inc., pp. 68-88, 278-317, 415-423, 1953.

8. Cooper, F. S., Liberman, A. M., Harris, K. S., and Grubb, P. M. Some Input-Output Relations Observed in Experiments on the Perception of Speech. Proceedings of the Second International Congress of Cyber­netics, 1958. Namur, Belgium: Association Internationale de Cyber­netique, pp. 930-941.

9. Pi.erce, J. R. and David, E. E. Man•s World of Sound. Doubleday, New York, 1958.

10. Peterson, G. E., Wang, W. S.-Y., and Sivertsen, E. Segmentation Tech­niques in Speech Synthesis. Journal of the Acoustical Society of America, 1958, Vol. 30, pp. 739-742.

11. Kryter, K. D. Human Engineering Principles for the Design of Speech Conmunication Systems. Report No. AFCRC-TR-58-62, Air Force Cambridge Research Center, Cambridge, Massachusetts, 1958.

12. P~terson, G. E. and Sivertsen, E. Objectives and Techniques of Speech Synthesis. L~nguage and Speech, 1960, Vol. 30, pp. 84-95.

13. Denes, P. B. a:;nd Pinson, L N. 1The Speech Chain. Bell Telephone Labo­ratori~s, pp. 163-192, 1963 ..

14. Orr, D. B., Firedman, H. L., and Williams, J.C. C. Trainability of Listening Comprehension of Speeded Discourse. Journal of Educational Psychology, 1965, Vol. 56, pp. 148-156.

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15. Woodson, W. E. and Conover, D. W. Human Engineering Guide for Equipment Designers. Second Edition, University of California Press, LTD., London, England, pp. 4-1 to 4-35, 1970.

16. Woodson, W. E. and Conover, D. W. Human Engi ne.eri ng GQ?i de for Equipment Designers. Second Edition, University of Caiifornia Press, LTD., London, England, pp. 2-80 to 2-89, 1970.

17. McCormick, E. · J. Human Factors Engineering. Thi rd Edi ti on, McGraw-Hil 1 Book Company, New York, pp. 201-223, 1970.

18. Van Cott, H. P. and Kinkade, R. G. Human Engineering Guide to Equipment Design. American· Institute for Research, Washington, D. C., pp. 123·...:223, 1972.

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D. Audio Information: Presentation Rates, Length, Context, Format, Style

1. Conrad, R. Acoustic Confusions and Memory Span for Words. Nature, Volume 197, pp. 1029-30, 1963.

2. Lawton, S. P. Principles of Effective Radio Speaking. Quarterly Journal of Speech, XVI, pp. 25p-277, 1930.

-·:;.

3. Pear, T. H. Voice and Personality. Chapman and Hall, London, 1931.

4. Ewbank, H. L. Studies in the Techniques of Radio Speech. From a speech delivered at the Third Annual Institute, Education by Radio, Columbus, Ohio, Quarterly Journal of Speech, XVIII, pp. 560-751, June 1932.

5. Lumley, F. H. Rates of Speech in Radio Speaking. Quarterly Journal of Speech, XIX, pp. 393-403, 1933.

6. Cantril, H. and Allport~ G. W. The Psychology of Radio. Harper, New York, 1935.

7. Lewis, D. Vocal Resonance. Journal of the Acoustical Society of America~ Volume 8, pp. 91-99, 1936.

8. Dunn, H. K. and White, S. D. Statistical Measurements on Conver­sational Speech. Journal of the Acoustical Society of America, Volume 11, p. 278, 1940.

9. Black J. W. and Mason, H. M. Training for Voice Communication, Journal of Acoustical Society of America, Volume 18, pp. 441-445, 1946.

10. Utley, C. M. Can A Radio Commentator Talk Sense? Paper presented before the Society for General Semantics, Northwestern University, Chicago, Illinois, March 1, 1946.

11. Miller, G. A. and Selfridge~ J. A. Verbal Context and the Recall of Meaningful Material. American Journal of Psychology, Volume 63, pp. 176-187, 1950 ..

12. Stevens, S. S. !!Handbook of Experimental Psychology, Chapters 21, 25, and 26, John Wiley and Sons, Inc., New York, 1951.

13. Miller; G. A., Heise, G. A., and Lichten, W. The Intelligibility of Speech as a Function of the Context of the Text Materials. Journal of Experimental Psychology, Volume 41, pp. 329-335, 1951.

14. Langefeld, H. S. Handbook of Experimental Psychology, Chapter 26, John Wiley and Sons, Inc., New.Jork, 1951.

:_"!-_

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15. Beighley, K. C. An Experimental Study of the Effect of Four Speech Variables on Listener Comprehension. Speech Monographs, Volume 19, pp. 249~258, 1952.

16. Pollack, I. The Information of Elementary Auditory Displays. Journal of the Acoustical Society of America, Volume 25, p. 765, 1953.

17. Pollack, I. and Ficks, L. · Information of Elementary Multidtmensional Auditory Displays. Journal of the Acoustical Society of America, Volume 26, p. 155, 1954.

18. Cherry, C. On Human Communication. Technical Press of M.I.T. and Wiley, New Yprk, 1957.

19. Smith, Malcolm, et al; Human Factors Analysis of Voice Communication Practices in Air Traffic Control, Volume 1, Final Report. Contract No. FAA/BRD-44, General Dynamics, Convair Division, Pamona, California, June 1960.

20. Miller, G. A. Language and Communication. McGraw-Hill Book Company, New York, 1963.

21. Conrad R. Acoustic Confusion and Irmediate Memory. Brit. J .• Psychol., Volume 55, pp. 75-84, 1964.

22. Hackworth, J. F. Auditory Short-Term Memory. Canadian Journal of Psychology, Volume 18, pp. 292-303, 1964.

23. Bar-Hillel, Y. Language and Information. Addison-Wesley, Reading, Mas_sachusetts, 1964.

24. Conrad, R., Freeman, P. R., and Hull, A. J. Acoustic Factors Versus Language Factors in Short-Term Memory. · Psychonomic Science, Volume 3, pp. 57-58, 1965.

25. Traul, G. N. and Black, J. W. The Effect of Context on Aural Perception on Words. Journal of Speech and Hearing Research, Volume 8, pp. 363-369' 1965.

26. Baddeley, A. D. Short-Term Memory for Word Sequences as a Function of Acoustic, Semantic, and Formal Similarity. Quarterly Journal of Experimental Psychology, Volume 18, pp. 362-365, 1966.

27. Liberman, A. M., et al. Perception of the Speech Code. Psychological Review, Volume 74, pp. 43.1-461, 1967.

28. Murray, O .. J. Articulation and Acoustic Confus,ability in Short-Term Memory. Journal of Experimental Psychology, Volume 78, pp. 679-684, 1968.

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29. Fell, J.C. and Laughery, K. R. Short-Term Memory: Mode of Presentation for Alphanumeric Information. Human Factors, Volume 11, No. 4, pp. 401-406, 1969.

30. Kryter, K. D. Methods for the Articulation Index. U. S. American Standards Institute, New York, New York, 1969.

31. Jaffe, J. and Feldstein, S. Rhythms of Dialogue. Academic Press, New York, 1970. ·

32. McCormick, E. J. Human Factors Engineering. Third Edition, McGraw­Hill Book Company, New York, pp. 185-200, 1970.

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E. Masking, Loudness, and.Audio Intelligibility

1. Steinberg, J. c. Effects of Distortion on the Recognition of Speech Sounds. Journal of the Acoustical Society of America, Vol. 1, pp. '" 121-137' 1929.

2. Fletcher, H.·' and Munson, W. A. Relation Between Loudness and Mask­ing. Journal of the Acoust.ical Society o.f America, Vol. 9, pp. 1-10, 1937.

3. Karlin, J. E., Abrams, M. H., et al. Auditory Tests of the Ability to Hear Speech in Noise. OSRD Report 3516, Psycho-Acoustic Laboratory, Harvard Univers.ity, 1944.

4. Kyster, K. D. and Stein, M. I. The Advantage of Clipping the Peaks of Speech Waves Prior to Radio Transmission. Report IC-83, Psycho­Acoustic Laboratory, Harvard University, 1944. (Summarized in Pro­modul at ion clipping in A&M Voice Communications. Journa.l of the Acoustical Society of America, Vol. 19, pp. 125-231, 1947).

5. Licklider, J. C. R. Effects of Amplitude Distortion Upon the Intelligibility of Speech. OSRD Report 4217, Psycho-Acoustic Laboratory, Harvard University, November 14, 1944. (Su11111arized in Promodulation clipping A&M Voice Co11111unication. Journal of the Acoustical Spci ety of A!Derica, Vo 1. 1 a, pp. 429-434, 1946}.

6. Gross, N. B. and Licklider, J. C. The Effects of Tilting and Clipping Upon the Intelligibility of Speech. Report PNR•ll, Psycho-Acoustic Laboratory, Harvard University, 1946.

7. Egan, J. P. and Wiener, F. M. On the Intelligibility of Bands of Speech in Noise. Journal of the Acoustical Society of America, Vol. 18, pp. 435-441, 1946. · · ..

8. French, N. R., and Steinberg, J. C. Factors Governing the Intel­ligibility of Speech Sounds. Journal of the ·Acoustical Society of America, Volume 19, pp~ 90-119, 1947. · .

9. Miller, G. A. The Masking of Speech. Psychological Bulletin, Volume 44, p. 105, 1947.

10. Egan, J. P. and Hake, H. W. On the Masking Pattern of a Simple . Auditory Stimulus. Journal of the Acoustical Society of America,

Volume 22, p. 622, 1950.

11. Miller, G. A. and Licklider, C. R. The Intelligibility of Inter­rupted Speech. Journal of the Acoustical Society of America, Volume 22, pp. 167-173, 1950.

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12. Garvey, w. D. The Intelligibility of Abbreviated Speech Patterns.· Quarterly Journal of Speech, Volume 39, pp. 296~306, 1953,

13. Pickett, J. M. Effects of Vocal Force on the Intelligibility of Speech Sounds. Journal of the Acoustical Society of America, Volume 38, pp. 902-905, 1956.

14. Hawley, M. E. and Kryter, K. D. Effects of Noise on Speech. Handbook of Noise Control, Mc~raw-Hill, New York, 1957.

15. Wathen-Dunn, W. and Lipke, 0 .. w. On the Power Gained by Clipping Speech in the Audio Band. Journal of the Acoustical Society of America, Volume 30, p. 36, 1958.

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ANNOTATIONS

A. REAL-TIME MOTORIST INFORMATION: BY AUDIO COMMUNICATION

1. Quinn, C. E. New Voice System Alerts Drivers~ Traffic Engineering, Ju,ly 1959.

A new comnunications system has been recently developed by the General Motors Research Laboratories for use as a driving safety aid. This system affords a means of bringing into a vehicle voice messages pertaining to emergency road conditions ahead. It utilizes the hitherto neglected induc­tion field,as a means of signal propagation and avoids the possibility of interfering with other radio services by operating at frequencies in the vicinity of 10,000 cycles per second. (author)

2. Hanysz, E. A., Stevens, J. E. and Meduvsky, A. Co11111unication System for Highway Traffic Control. Electronics, October 1960.

Communication of voice messages to motorists passing roadside stations has long been considered ~s an aid to safer highway travel. Electromag­netic radiation would be convenient for such a link. However, the inabil-· ity to confine radiation to the exclusive use of a select group of vehicles defeats its practicality. Microwaves are more directional, but not simple.

A comnunication system consisting of an induction radio link operating in the vlf band may be the answer to the driver aid problem.- Termed Hy­Com, the system was conceived by the General Motors- Res·earch Laboratories and uses a loop transmitting antenna a1ongside the road to set to an ampli­tude-modulated magnetic induction field over the highway adjacent to the loop. Vehicles with receivers pick up the message as they pass through the field. (author)

3. Weinberg, M. I., Deley, M. J. and Schneeberger, R. F. Surveillance Methods and Ways of Comnunicating with Drivers. NCHRP Report 28, 1966.

Although the initial freeway concept was developed on the premise that traffic would operate unhindered by traffic controls, it is now apparent that properly designed control systems will improve the freeway~s ability to service the ever-increasing traffic demand. This research was initiated to consider closed-loop control systems. The surveillance schemes utilized must be capable of diverting the traffic attempting to use the congested facility onto alternate routes. Three types of closed-loop surveillance systems have been studied in depth.

Of particular interest is the second surveillance system which concerns the effectiveness of using an airborne observer to control traffic. Radio broadcasts were used to inform the motorists of the most desirable traffic routing and cost studies were made utilizing a light airplane and a heli­copter.

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4. Dudek, C. L. and Jones, H. :G. Real-Time Driver Information Needs for Urban Freeways. Texas Transportation Institute Research Report 139-4, July 1970.

To broaden the application of real-time freeway operations systems, the Texas Transportation Institute and the Texas Highway Department, in cooperation with the U. S. Department of Transportation, began a research project entitled "Freeway Controi and Infonnation Systems".· One of the objectives of the project was to.d~velop functional requirements for a freeway communications system. Toward this end, a questionn.aire survey was conducted in the cities of Houston and Da 11 as. This report~' discusses the results of the survey which was directed at the evaluation of the following:

1. Driver attitudes toward the need for real-time freeway information 2. Potential use of and response to real-time freeway information 3. Driver preferences for mode of communitation . . 4. The type of information desired by the freeway driver 5. Driver priorities regarding the locations where information would

be most useful 6. Driver comprehension of and preferences for visual displays

(author)

5. Case, H. W., Hulbert, S. F. and Beers, J. Research Development of Changeable Messages for Freeway Traffic Control: Final Report August 1971. ITTE, School of Engineering and Applied ~cience, UCLA.

This study reports on the testing and evaluation of various candidate message fonnats eventually to be used in audio and sign advance freeway traffic advisory systems. ·It also reports on subsequent interrogation of drivers tested on the UCLA Sign Tester, in the Audience Studies, Inc. Pre­view House, and in the UCLA Driving Simulation Laboratory. The following is a summary of conclusions.

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(a) Drivers overwhelmingl/ approved of the concept of an advance free­way traffic advisory system despite its obvious cost.

(b) ·Drivers evaluated both sign and audio systems more favorably' than unfavorably, but consistently indicated a preference for a sign · system over an audio system.

(c) Either sy5'tem will favorably modify driving behavior of the major­ity of drivers, but the "authoritative" nature of the sign system exhibited the greatest level of behavior modification, including frustration reduction.

(d) The content of the messages should be short,.simple and"contai.n specific, actionable information.

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(e) Driver preferences for types of infonnation to be given were (in order): lane blockage, distance to blockage or problem, length of delay, reason for delay, location of problem by ramp name. ·

(f) Lane numbers confused.drivers (lane #1 was identified as both median and outside lane).

(g) "Middle lanes" confused drivers (identified as both median lanes and center lanes in your direction of travel).

· (h) Drivers prefer the word "nonnal" to a blank sign as the latter was seen as being too ambiguous.

(1) It will be difficult to prepare audio messages which are neither so repretitive as to be boring, nor so complex as to be misunder-stood. ·

(j) Messages including a reference to specific miles-per-hour tend to elicit dangerous overreaction {deceleration) from drivers.

6. Mccasland, W. R. "Freeway Control and Infonnation Systems, Texas Trans­portation Institute Research Report 139-13F, January 1972.

A study of urban traffic operations was conducted on the Gulf Freeway in Houston. The study investigated those areas which give greatest promise for immediate implementation to relieve traffic congestion and to improve safety for the largest number of urban motorists. The major areas of study were: traffic control, detection and clearance of disabled vehicles, and driver communications. Although not all objectives were completed, a re­view of the accomplishments of the studies is presen1;,ed· with references to the 13 reports, five papers, and other material prepared during the course of the project. (author) •

7. Guide, to Highway Communications Systems Technology and Design. Report FHWA-RD-75-101, Federal Highway Administrati~n, Traffic Systems Division, January 1975.

This paper is intended to serve as a technical aid in the understanding of the design of highway communiCation systems (also referred to as traffic surveillance and control systems). It is expected to provide background and insight into the many technical decisions which must be-made---for--a .good system design. It presents design alternatives in most cases and provides a rationale for selecting the approach which is hopefully best for any given system.

A second purpose of this paper is to indicate the present state-of-the art (accepted techniques or practices) of the communications aspects of traffic surveillance, control, and motorist information systems.

The paper is organized into three major topics: Data Sources; (2) Displays; and (3) Cermnunications.

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(1) Infonnation and This organization

presents the reader and user with an o~derly approach to the subject. Additional emphasis is placed on the topic of conmunications, since a detailed coverage of it was a major objective in writing this paper. (author.)) ·

8. Gatling, F. P. Auditory Message Studies for Route Diversion. Federal Highway Administration, June 1975.

Four studies on auditory messages to motorists are reported. The re­sults in Studies 1 and 2 indicat~ that drivers can handle up to four units of route information successfully. When the messages contain more than four units of information, drivers make unacceptably large numbers of errors when attempting to follow a route. Study 3 showed that drivers could choose and retain general information from auditory messages in which they had an interest and that the difficulty of the message was increased as exit and route numbers were increased. Study 4 developed information on the lead: distances that visual signs alerting motorists of the availability of audi­tory informatton need to be placed from the broadcast areas. (author)

9. Gatling, F. P. The Effect of Auditory and Visual Presentation of Navi­gational Messages on Message Retention. Federal Highway Administration, June 1976.

Navigational messages containing from two to seven units of information were presented to three.groups of subjects. One group of subjects received the messages after they had seen an alerting sign and,. in response to the sign, tuned the radfo to a specified frequency to ·rec-e1ve the message (man­ual group). A second group received the messages automatically and aurally (automatic group). The third group received the information visually. The manual group did consistently poorer on message retention than the other two groups. There was no difference in message retention between the aural automatic group and the visual group. (author) .

10. Carvell, J. D. and Hatcher, D. R. Evaluation of a Dial-In Traffic Information System, Report RF 953·25A, July 1976.

Various methods of providing information to the driver: a) before beginning his trip; b) during his trip to the freeway; and c) while on the freeway, have been considered and/or implemented. This report documents one of these methods: pre-trip information via a dial-in information system.

Since various information sources were available through the ongoing corridor control project, implementation and testing of this system was enhanc~d. Although not originally considered in the corridor project development, the sponsor's desire to test such a system was readily incor­porated into the overall study. (author)

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11. Gordon, D. F., Gatling, F .. P. and Harris, R. D. Auditory Communica­tion of H.ighway Information. Draft Report, Traffic Systems Division Office of Rese.arch, FHWA, undated.~ ·

This study consists of a review of the factors which need to be con-· sidered in a complete audio transmission system which consists of the warn­ing and the verbal message,·aJong with any repetition of the verbal message. The general topics discussed are detection of an audio signal, intelligi­bility, understandability, behavior mpdification of drivers by verbal mes­sage, and driver opinion of audio signing.

In detennining the warning tone, careful consideration must be devoted to frequency, intensity, and type of tone. Intelligibility can be improved by increasing contextual cues, avoiding bad sound combinations, and manipu­lating physical parameters. Comprehension is concerned with the ability of the listener to understand the meaning of the messages. The fonnat of the message should be formal and avoid using colloquialisms. The only parame­ter for which the audio system rated more favorably than signs for the total audience was that for providing the most up-to-date information.

12. Technical Considerations Regarding the Implementation of a Low Power Roadside Transmitting System at Broadcast Frequencies. Federal Highway Administration, undated.

Highway advisory radio systems op~rating at standard broadcast frequen­cies offer a practical means of conmunicating information to motorists since perhaps more than 90 percent of all vehicles in ~.he tr.. S. today are equipped with standard AM receivers. The development of such a highway radio ·system is, therefore, only that of the roadside transmitting system which involves the application of several well-established principles of antenna and network theory and radio-wave propagation.

The purpose of this paper is to present a brief review of the technical and engineering aspects that shou.l d be considered in the design and i nsta 1-1 ati on of low-power transmitting systems that are to operate at standard broadcast band frequencies. (author)

13. Halstead, W. S. Roadside Radio in Theory and Practice. American Asso­ciation of State Highway Officials, undated.

The subject of this paper is directed primarily to the mode of operation and results. obtained by an integrated, multi-function, cable system for driver information a·nd traffic surveillance. The system utilizes a special­ized form of triaxial !=able designed for direct burial in earth on the side of the highway, or within the roadway structure itself. Such a system has now been in successful public operation at the Los Angeles International Airport for the past year. Application of the same type of system on free­ways or other heavily traveled highways also is given consideration in this paper. (author) .

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B. HIGHWAY RADIO SYSTEMS

1. Halstead, W. S. Electronic Communications on Highways. American Associ atiion of State Highway Offi ci a 1 s: Conmi ttee Proceedings, pp. 150-153, 1957.

While standard broadcast stations in the larger cities have peen em­ployed to supply motorists with general reports on traffic conditions, more effective methods reside in the application of localized, restricted­range transmission systems which may be installed at strategic points along highways and· operated directly by the traffic authorities who carry the responsibility for control of traffic movements on specific highways. Localized radio transmission systems of this general type which confine. their effective signals within a designated zone along a highway by uti-1 izing the induction field that surrounds a wayside cable on which radio­frequency energy is impressed, have been tenned "induction radio" systems. Drivers are alerted to the presence of the induction radio system and advised of the frequency employed by a distinctive sign or series of signs in advance of the radio zone. Applications of this system of information transmittal are extensive and far-reaching.

2. Keller, J. E. The FCC and Radio Control of Traffic Control Devices. Traffic Engineering, May 1959.

This paper discusses the Federal Conmunications Commission actions toward the development of radio traffic signal control. The contention is that this would proceed in a more orderly manner if specific frequen­cies were allocated for this purpose through the establishment of a new service. This new Traffic Signal Control Radio Service would be allocated certain frequencies or frequency bands. The main context of this article is concerned with what frequencies or frequency bands should be requested.

3. Dudek, C. L., Friebele, J. D. and Lautzenheiser, R. C. Evaluation of Conmercial Radio for Real-Time Driver Conmunication on Urban Freeways. Highway Research Record 358, 1971.

Driver preferences were measured through a questionnaire survey to evaluate the potential of commercial radio for providing real-time free­way traffic information to drivers in urban areas. In addition, traffic reports given by three radio stations in the Houston area were monitored to evaluate the reliability, accuracy, and timeliness of current traffic broadcasts. The results of the study suggest that commercial radio could play an important role as part of an effective real-time traffic informa­tion system for urban freeway drivers. However, traffic reports as cur­rently broadcast by the three radio stations monitored in Houston would not be completely satisfactory for the system being considered. Improve­ments in the reliability and timeliness of the traffic information pro­vided would be necessary. (author)

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4 .. Covault, D. 0., Dervish,.J. arod Kanen, A. C. Study of the Feasibility of Using Roadside Communicatior.s for Traffic Control and Driver lnfor_. mation: .Report No. 2. Highway Research Record 202, pp. 32-66, 1967.

A method of driver-roadside communication was tested on the Atlanta Freeway System during daytime and nighttime driving activitie~ in 1964 and 1965. The two related studies attempted to evaluate the effectiveness of roadside radio conmunication on behavior of the driver as related to his execution of a diverging maneuver from a freeway traffic system. The radio system, called Hy-Com, provides radio communications from the road­side to the driver and· consists of a car~mounted receiver and a roadside transmitter.

Volunteer participants were randomly assigned to any one of various test conditions. Each test condition provided guidance information of varying degrees of adv~nce and exit infonnation by using highway signing, radio conmunication or combination of both. While information was being given to participants in each test condition, data on traffic character­istics of the driver were collected at various positions along the freeway and the deceleration lane prior to an exit ramp selected for the study. Time-lapse motion photography, the BPR traffic analyzer, and manual recording were used.

Analysis of variance and multiple range test techniques were used to determine differences between driver performances under different levels of infonnation provided during the running of each test condition. The results indicated that audio messages were as effective as visual messages and when given together, the performance of t~st drivers was generally better than that of test .drivers with only visual or· audio messages. Indications were that a radio-signing system which will provide the neces­sary in.formation where needed, can be effective and at the same time, avoid extensive over-signing. Additional research is required to deter­mine the use of radio as a communication devi.ce on a system basis. (author}

5. Bauer, H. J., Quinn, D. E. and Malo, A. t. · Response to a CB Radio Driver Aid Network. Highway Research Record No. 279, 1969.

The need for a method to provide surveiilance of roadways has gener­ated_ research for many agencies, including the General Motors Research Laboratories (GMR}. The Detroit Department of Streets and Traffic is currently operating ttiae GM-sponsored CB Radio Driver Aid Network. This system makes possible the reporting of traffic-related information such as accidents and traffic flow interference. On the basis of earlier demonstration efforts, the system has been expanded to cover the entire Detroit system of surface streets and freeways. The specific functional aspects of the system and a description of its major technical equipment are given ..

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The paper discusses the results of the earlier operations, presents data on current operational activities, findings of a questionnaire sur­vey, and reactions and conclusions resulting from these efforts. The sys­tem is viewed as providing a feasible interim solution to the problem of roadway surveillance, incident reporting, and action implementation to provide safe and efficient traffic flow. (author)

6. Dudek, C. L. and Cummings, D. i.Application of Commercial Radio to Freeway Communi cations - A Stut!,y of Driver Attitudes. Texas Transpor­tation Institute Research Report 139-3, 1971.

Ramp metering has proven to be an effective means of improving the operational efficiency of an over-crowded urban freeway. Freeway control systems can now prevent a breakdown under 11 normal 11 conditions. However, adequate control of demand under "abnormal" conditions, such as accidents or lane blockages, is not feasible. Real-time driver communications is therefore, necessary to increase safety and efficiency.

One method of transmitting information to the driver is through the use of commercial radio. This study discusses the results of a question­naire survey directed toward the evaluation of commercial radio for real­time f~eeway communications. The conclusion is reached that commercial radio could play a vital role as part of an effective real-time traffic information system for urban freeways. (author)

i 7. Quinn, C. E. A Highway Communication System for the Motorist: The

Case for Two-Way Radio. Highway Research Record No. 402, 1972.

The author briefiy reviews the communications systems currently in operation and those proposed by highway departments for users of American highways who find themselves stranded or in need of information. The paper reports on the volunteer two-way mobile voice radio. system that has been developing in the U. S. in the 27 MHz Citizens Radio Service. The author proposes that a highway communication radio service be set up by federal agencies. The principal intent of this service is for aid to the motorist and for contact with him by highway, law enforcement, and other public service agencies. It is suggested that this service be implemented on an interim basis in the 26 to 30 MHz band using voice communication and readily available, inexpensive transceivers for communication on the emer ... gency channel 9 of the CRS and on a minimum of five adjacent channels. No change in FCC citizens Class D license should be required. In conclusion, recommendations are made for the development of the hardware and implemen­tation of the radio system. (author)

8. Chiaramonte, R. M. and Kreer, H. B. Measuring the Effectiveness of a Volunteer Emergency-Monitoring System in the Citizens Radio Service. Highway Research Record No. 402, 1972.

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This paper describes the experimental statewide emergency conmunica­tions network utilizing the Citizens Radio Service conducted in Ohio during 1970-1971. A joint project of REACT National Headquarters and the Ohio State Highway Patrol, the program known as the Ohio REACT Emergency Network, was established as an experimental two-year program to test the effectiveness of volunteer citizens monitoring emergency communications and providing assistance to motorists in accordance with the Federal Com­munications Convnission's establishment of channel 9 as the official emer­gency channel. A state director was appointed for REACT and districts were established, based on the Highway Patrol district boundaries. A dis­trict coordinator was appointed for both the Highway Patrol and REACT volunteers in each district to provide comparable levels of contact and authority. Log reports of calls received for emergencies and motorists' assistance are tabulated by computer at General Motors Research Labora~ . tories. This paper describes the organization, presents the data gathered in the program's first year of operation, and establishes goals for the second year. (author)

9. Stephany, S. J. Conunents to a paper by Chairamonte, R. M. and Kreer, H. B. Measuring the Effectiveness of a Volunteer Emergency-Monitoring System in the Citizens Radio Service. Highway Research Record No. 402, 1972.

The need for communication with the motorist has been concluded in various studies and analyses conducted under government sponsorship during the last decade. Collectively, the studies are .diverse in subject and scope, covering many aspects of highway communication and ranging from the fundamental need to receive information to accident detection and location, reporting highway hazards, and coordination of public service agencies. It has been conservatively estimated that 50 to 75 percent of rural high­way deaths need not have occurred if prompt and experienced emergency medi­cal service had been available. Motorist communications must be provided for safety and.efficiency in highway travel, in addition to the other potential benefits to the American public.

The ultimate solution to the accident assistance problem lies in a system that will enable the motorist to summon assistance from his car and be warned of hazardous conditions before reaching the point of danger. The system should also provide automatic detection and location for acci­dents, even if vehicle occupants are unable to do so; vehicle-to-vehicle communication to warn of approaching ambulances, fire trucks, and the like; and the capability for the highway safety system to conmunicate at will with vehicles requiring assistance.

Electronic advances and state-of-the-art developments can now meet these needs. The crucial task of integrating these developments trito an effective national system is more political, institutional, administrative, and managerial than technical. The need is clearly demonstrated by acti­vity of volunteer citizen groups such as REACT, who, once given the means

21

to communicate via two-way radio, have instinctively developed their own highway co11111unications system. (author)

10. Anderson, R. A. and Robertson, R. G. Study and Development of Highway Advisory Information Rad1o. Atlantic Research Corporation. Research Report No. FHWA-RD-74-73, December 1974.

A complete Highway Advisory Information Radio (HAIR) system was devel­oped for audibly conveying traffic advisory and emergency information to the motoring public using a low power, limited coverage roadside transmit­ter at dedicated frequencies of 530 kHz and 1606 kHz. Types of informa­tion conveyed include emergency messages, warning tones. indicating the approach of an emergency vehicle, advisory messages to alert motorists of anomalies ahead and alternate routes, and trip needs such as information pertaining to gas, food, and lodging services. A major objective of the program was the development of special automotive receivers permitting the motorist to automatically receive the traffic messages while listening to his favorite AM or FM broadcast station. The radio transmission system utilized audio tone codes to achieve control of the automatic receivers; however, the system also pennitted message reception with over 90 percent of existing AM automobile radios.

Surveys of commercial automotive AM receivers were made to determine tuning range limits and receiving sensitivities at 530 kHz and 1606 kHz. It was found that the capability of automotive AM radios to receive out­of-band signals depends almost entirely on field strength and not on the limits of tuning range. (author)

11. Lampert, S., Hulbert, S., and Jenkins, A. Restricted Range Radio Information System Evaluation Study. Institute of Safety and Systems Management, USC. Prepared for Los Angeles Department of Airports, Los Angeles, California, April 1974.

In August 1973, the Los Angeles Department of Airports initiated a program with the University of Southern California Research Center for Safety and Systems Management, to evaluate the Restricted Range Radio Information Service at Los Angeles International Airport. The intent of the study may be briefly stated in terms of the following objectives, namely:

(a) Determine the public's acceptance of the Restricted Range Radio Information System at Los Angel es International Airport.

(b) Evaluate the effectiveness of the Auditory Displays (broadcasts) as they affect traffic at Los Angeles International Airport.

(c) Provide recommendations for improvement to the present system.

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For this evaluation, questionnaf"re-type surveys, both at the Airport and at the Pre Vue House in Hollywood, were conducted to determine the user's knowledge of the service.and to. gain his reactions as to its use­fulness~ Additionally, direct observations and tests were conducted at the Airport in an attempt to assess· the listener population·on a given day. The results of these findings, alo_ng with attendant conclusions and recommendations, are presented in this report.

In terms of acceptance, better than 75 percent of· the 11 1 istener dri­vers" fo111nel·the.service· useful, while·approxilnitely 55 percent of all motorists felt it would be useful to them in the future. Of this same sample, 52.3 percent said they would recommend the service to others. Another sample, which included a large fraction of frequent private auto motorists, indicated that 75 percent would recommend the service. Addi­tionally, more than 56 percent of the frequent users rated the radio ser­vice ·good to excellent, while 19 percent rated it as having limited value, and 5 percent, no value.

The utility of the radio infonnation system for purposes of traffic control is directly proportional to its listening audience. In this re­gard, the need for inc:reasingthe 11 knowledgeable driver11 population is critical i-f this s-ervice is to fulfill its expectation. This is needed to insure a large enough •ilistening driver 11 population among all motorists during the peak traffic periods. Precisely the periods for which the radio information service was intended and for which times its impact for improving traffic flows is critical.

12. Trabold, W. G. and Reese, G. H. Performance of Volunteer Monitors Using .Citizens Band Radio for a Highway Communications Service. Transportation Research Record No. 495, 1974.

A two-year study of the performance of Ohio REACT volunteer monitors using Citizens Band (CB) radio to provide a highway and emergency communi­cation service has been completed. The report describes how CB radio is used for aid and information purposes. Measured performance data are used to analyze monitoring coverage in the statt. It is shown that in Ohio volunteer CB monitors anhually contribute a public service having an eco;.. nomic value of approximately $10.2 million. (author)

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C. SPEECH, HEARING, AND COMMUNICATION TECHNIQUES

1. Munson, W. A. Relation Between the Theory of Hearing and the Inter­pretation of Speech Sounds. Journal of the Acoustfoal Society of America, Vol. 17', p. 103, 1945.

The theory that the ititerpretation of speech sounds is largely depend­ent upon differential sensitivity, i.e., the ability of the ear to detect small changes of pitch and intensity, is used as a basis for predicting the results of intelligibility tests~ By use Of'empirical methods, a functional relation is obtained between the energy distributionofspeech, the differential sensitivity of the ear, the masking properties of sounds, and the number of correctly preceived syllables in an articulation test. A comparison is made of the empirical functions and the corresponding fundamental speech and hearing characteristics. It was found that in most instances, computed i ntell i gi bi 1 i ty compared favorably with experimenta 1 results, but in a few cases large discrepancies were nGted. (author)

2. Beranek, L. L. The Design of Speech Communication Systems. Proceed­ings of the Institute of Radio Engineering, Vol. 35, pp. 880-890, 1947.

A method is presented for calculating the ability of a communication system to transmit speech intelligibly in the presence of noise. The total speech arriving at the ear of a listener is detennined by adding the orthotelephonic gain of the system to the speech spectrum which would be produced by a talker at the eardrum of a listener at a distance of one meter. The total noise arriving at the ear is detenn-ined in terms of its spectrum 1eve1 froin measurements of the noise pi ck up·- of the microphone and the acoustic attenuation of the earphone cushions. The area lying between the spectrum level of the peaks of the speech and the spectrum level of the total noise arriving at the eardrum when plotted on a distorted fre­quency scale, determines a quantity called articulation index which can be correlated with articulation scares. Methods for detennining the maximum gain permissible·in the system are discussed. The validity of the method is established by comparison of calculated, with carefully measured articu-1 ati on, scores. {author)

3. Langfeld, H. S. Handbook of Experimental Psychology. Chapter 26, John Wiley and Sons, Inc., New York, 1951.

Although the perception of speech is a psychological problem, it re­mained for telephone engineers interested in the adequacy of their equip­ment to develop procedures for the quantitative investigation of speech perception. These procedures were evolved, principally by the Bell Tele­phone Laboratories, without reference to the traditional problems and methods of experimental psychology. The concern was with intelligibility rather than perception, and the results were used to evaluate equipment rather than listeners.

24

i . ;

The following topics were investigated: . .

(a)

(b)

(c)

(d)

(e)

(f)

(g)

{h)

Acoustic Characteristics of Speech Quantitative Evaluation of Intelligibility Relation Between Intensity and Intelligibility The Masking of Speech ., Empirical Equation for Articulation

' Amplitude Selectivity I ndi vi dua 1 Differences · Practical Applications.

All significant find.ings are presented in graphical and tabular form.

4. Fletcher, H. Speech and Heari.ng in Communication. D. Van Nostrand Company, Inc., pp. 68-88, 278-317, 415-423, 1953.

Chapters 4, 15, 16, and 18 discuss the topics of acoustical speech powers, methods of measuring the recognition aspect of speech, proficien­cies of talker-liste,ner pai·rs, and effects of distortion on individual speech sounds. Of particular interest are the relationships exhibited : between men's and women's voices as to pitch, quality, and voice power. Detailed studies are reviewed and results graphically elaborated.

5. .Denes, P. B. and Pinson, E. N. The Speech Chain-. Bell Telephone Laboratories, pp. 163-192,. 1963.

This chapter is specifically (:Oncerned with speech recognition. During speech, our vocal organs produce ·sound waves with many different character­istics: different intensities, different durations, and different spec­tral components. Just because our vocal organs produce a variety of fea­tures, does not mean that they a re .a 11 needed for i ntell i gi bi 1 ity. What conditions are necessary for satisfactory speech recognition? Are all the components of the speech spectrum essential to recognition and; if not, which are the important ones? How far can we reduce the intensity of the speech wave without undennining intelligibility? These and similar ques­tions are all discussed ·in this chapter.

Experiments for pin-pointing the speech wave features important to speech recognition were also performed. These fall into two classes. First, there are experiments in which we use the speech waves produced by a person speaking normally. We alter some of the acoustic - - - · features of this naturally produced speech, and ask someone to listen to the modified sound to detennine how far its intelligibility differs from that of the original speech. In the second class of experiments, we generate a speech-like wave artificially. With little trouble, we can

25

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separately adjust each acoustic feature of this artificially produced speech. Consequently, artificial {synthesized) speech is particularly suitable for speech recognition studies. (author)

6. Woodson, W. E. and Conover~ .D. W. · Human Engineering Guide for Equip­ment Designers. Second Edition, University of California Press, Ltd., London, England, pp. 4-1 to 4-35, 197D.

This chapter is primarily interested in the auditory system (ear and associated neurology) from the standpoint that this is an unalterable fact; therefore, sound systems (radio transmissions) should be designed to conform most efficiently to the auditory system. Background auditory information fundamental to the development and application of these princi­ples is reviewed.

7. Woodson, W. E. and Conover, D. W. Human Engineering Guide for Equip­ment Designers. Second Edition, University of California Press, Ltd., London, England, pp. 2-80 to 2-89, 1970.

Audio techniques for the display of information have not been utilized to the fullest extent in equipment design. Auditory signals in conjunc­tion with visual signals, however, in some instances have demonstrated a decided advantage over either type of signal alone. The major advantage of auditory signals is the fact that an operator can act upon the infor­mation he receives without physically facing the source of the signal. The human auditory-perception system is a very capable discriminator of wanted versus unwanted sound and is ideal for sorting usable signals from noise. Certain cautions must be take~ in the use of the auditory display, however.

This chapter dis(:u,ssed proper and improper auditory display techniques . •

8. McCormick, E. J. Human Factors Engineering. Third Edition, McGraw­Hill Book Company, New York, pp. 201-223, 1970.

When feasible, of course, speech communications should be carried out under favorable conditions, uncluttered with noise. However, in many circumstances, it is not possible to reduce noise at its source. Under these and other circumstances it is necessary to look to other elements of the total comnunication system, rather than to the noise source, itself, for poss i bili ti es of improving the i nte 11 i gi bi l i ty of speech. On the engineering design side of the coin, the possibilities to consider are those of minimizing the transmission of noise if possible, improving the design of the communication equipment, and modifying the nature of the messages to be used; and on the personnel side of the coin, the possibili­ties are those of selection and training of talkers and receivers, where these are feasible.

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The speech chain comprises different forms or levels in which a spoken message is transmitted, including a linguistii:ennd physiological level of the speaker, an acoustic level of the transmission system, and a physio­logical and linguistic level of the receiver.··. The types of phonemes that can be_ generated by the human speech mechani sm.s are:

(a) • plosives, or stops {b) fricatives, or spirants (c) laterals (d) trills (e) vowels

The English language has about 38 phonemes out of many hundreds that peo­ple can generate. Phonemes vary from one another in their spectral char"" acteristics, including the combination of frequencies and intensities.

Speech intelligibility tests can serve such purposes as (a) to evalu­ate the adequacy of a communication system, (b) to determine the communi­cation efficiency of individuals within a system, and (c) to determine hearing loss or speech.

In evaluating the adequacy of communication systems, the AI can be used to estimate the intelligibility of speech. An Al, in turn, can be converted into an intelligibility score, which is the estimated percentage of the spoken material that can be understood under a given set of condi-ti ans. · --

The SIL is an index of noise level (specifically the average of three octave bands); it is used as a measure of the destructiveness of noise in the reception of speech. · ·

- The NC curves are sometimes·used as the'basis for recommendations of permissible noise levels for specific communication situations. The intel­ligibility of speech under adverse conditions depends in part on the na­ture of the message, including its vocabulary, its context, and its phone­tics.

. Different types of distortion of speech can be caused (intentionally or unintentionally) by the transmission system; however, the intelligibi­lity of speech does not depend on high fi.delity. The effects of filtering depend on the frequencies that are filtered out by either high-pass or low­pass filters. Center clipping affects intelligibility much more than peak clipping.

9. Van Cott, H. P. and Kinkade, R. G. Human Engineering Guide to Equip­ment Design. American Institute for Research, Washington, D. C., pp. 123-223, 1972.

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Chapter 4 emphasizes heari_ng and the presentation of auditory signals. Guidelines are provided for when and how to present each type of auditory or other sensory information. The perception of sound, the problems of masking and its reduction, and the choice of single and multiple signals are covered~ Some information is_ given on other senses as media for in­formation presentation. Speech as a mode of information presentation is discussed in detail.

Criteria for equipment design to enable human speech communication are the major concern of Chapter 5. Measurements of fundamental speech sounds­their pressure, range, and level, as well as ways of measuring intelligibi­lity through actual testing or through calculation, are presented. Prob­lems of noise and reverberation, and protection against them, are also discussed as well as how components can aid intelligibility through gain control and peak clipping. Special design problems covering requirements of multi-channel listening, communication in unusual environments, through masks, and using bandwidth compression, are all considered, concluding with the human criteria of communication performance, trainability of persons, language factors influencing intelligibility, and the necessity for feedback.

10. Covault, D. 0. and Bowes, R. W. A Study of the Feasibility of Using Roadside Radio Communications for Traffic Control and Driver Informa­tion. Annual Report No. 1, Engineering Experiment Station, Georgia Institute of Technology, February 1964; also, Highway Research Record 49, pp. 89-106, 1964.

A new method of roadside communicatior with the driver incorporates car-mounted receivers and road$ide transmitter installations. The primary aims of the research project were to measure the effectiveness of this as a traffic control and driver information device, to judge its acceptabi-1 ity by the driving public, and to arrive at a preliminary cost for the implementation of such a system.

,. Half the vehicles .selected were used as test group and half as control

group for each of three experiments in which the test group drivers received radio informationon accidents and typical maintenance activities. In-the route information experiment no control group was used. Both test and control group drivers ~eceived similar information from signs and other signals where they were employed. Data on traffic flow were col­lected using time-lapse motion picture photography at locations just beyond the points of information reception. In addition, test vehicle operators were interviewed at the end of 10 miles of the test section to determine their reaction to the radio communication.

Results of the experiments showed that radio communication is effec­tive in controlling vehicle speed in hazardous areas. The difference in the lateral placement distribution between the test and control vehicles immediately prior to the hazardous areas was significant in some of the

_experiments. The route information given in one of the experiments was

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considered by drivers to be helpful and a possible future use of the radio system~ Interview data revealed that the motorists considered

· radio co11111unication useful and that it should be used in a variety of situations to provide a variety of information~ Driver acceptance was indicated by the amount drivers were willing to pay for a radio receiver capable of receiving roadside oomnunication, based on the assumption that this receiver would be constructed as an integral part of the usual car radio and would operate if the car radio was oo or off. (author)

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D. AUDIO INFORMATION:. PRESENTATION RATES, LENGTH, CONTEXT, FORMAT; STYLE

l~ Lawton, S. P. Principles ofEffecti've Radio Speaking. Quarterly Journal of Speech, XVI, pp. 255-277., 1930.

The principles of effective radio speaking are set down in this paper primarily considering the important statements, studies and experiments from 1920 to 1930, concerning spea~~;i.ng over radio, as well as.the tabula­tion of answers on questionnaires filled out by radio listeners. The results are discussed and presented in appendix form with interest on choice of subject, unity, sentence structure, speech length, vocabulary, volume, extraneous noises, pitch, enunciation, and pronunciation.

2. Ewbank, H. L, Studies in the Techniques of Radio Speech. From a speech delivered at the Third Annual Institute, Education by Radio, Columbus, Ohio, Quarterly Journal of Speech, XVIII, pp. 560-571, June 1932,

There ts a need for research to determine the factors which influence successful styles of radi·o speaking. The three following problems are dis­cussed in detail:

(a) What is the relationship between formal and informal broadcasting presentation and dialogue as to effectiveness of giving informa­tion over the radio?

(b} What is the best rate for speaking over the radio? Does it vary with the individual? For the same individual, does it vary with the material? Does it vary with the desired audience response?

(c} Should the radfo speaker use a uniform rate? Or should he vary the rate as much as possible?

3, Lumley, F. H. Rates of Speech in Radio Speaking, Quarterly Journal of Speech, XIX, pp. 393-403, 1933.

In this study the average syllable and word rates of speech for persons talkin.goverthe radio were determined. The average syllable rate was roughly 240 per minute and the word rate 160 per minute. Slight differences were shown to exist between the rates of delivery for speakers addressing adults and those addressing school children. Figures for news talks showed that they were delivered at a faster rate than other talks. Variations in rates were roughly the same for all classes of talks studied. (author)

4. Lewis, D. Vocal Resonance. Journal of the Acoustical Society of America, Vol. 8, pp. 91-99, 1936.

The purpose of this paper is to describe a procedure for investigating the resonance properties of the vocal cavities and to summarize data

30

already secured. In general, the procedure involved a determination of the harmonic structure of waves selected from among those within stngle pitch vibrato cycles of sustained vowels. The analytical data were then treated in such a way as to throw light on the characteristics of thefvocal resona­tors. (author}

5. Black; J. W. and Mason, H. M. Trainin~ for Voice CoJllll1unication, Jour ... nal of Acoustical Society of America, Vol. 18, pp. 441 .. 445, 1946.

A training program was devised for improving the intelligibility of Army ... Air Force personnel in talking over the interphone and radio. The contents of the course, amount of training required, and the training requirements were determined experimentally. This paper summarizes the re­sults of the over ... all program and compares them with the improvements that accompanted ttpartial~ training, particularly tn voice loudness and preci­sion of arttculatton~ (authorJ

. ' 6, Utley, c. M. Can a Radio Commentator Talk Sense? Paper presented

before the Society for General Semantics, Northwestern University, Chtcago, 111 inoi .. s, March 1, 1946.

The author conments extensively, from his many years of experience, on the qualifications and charactertstics of a good radio announcer or commen .. tator. The problems and pitfalls of radio announcing are discussed with two critical areas being that of false impression and effective communica-tion of ideas. - -

7. Miller, G. A. and Selfridge, J. A. Verbal Context and the Recall of Meaningful Material. American Journal of Psychology, Vol. 63, pp. 176-187, 1950.

A quantitative definition for verbal context is described in this study in terms of dependent probabilities. The definition is used to construct lists of words with varying degrees of contextual determination. When short-range contextual dependencies are preserved in nonsense material, the nonsense is as readily recalled as is meaningful material. From this re­sult it is argued that contextual dependencies extending over five or six words permit positive transfer, and that it is these familiar dependencies, rather than the meaning per se, that facilitate learning.

8. Miller, G. A., Heise, G. A, and Lichten, W. The Intelligibility of Speech as a Function of the Context of the Text Materials. Journal of Experi·mental Psychology, Vol, 41, pp. 329-335, 1951.

For many years communication engineers have used a psychophysical method called the ·~artkulation test". An announcer reads lists of syllables,

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words, or sentences to a group of listeners who report what they hear~ The articulation score is the percentage of discrete test units.reported correc .. tly by the listeners. This method gives a quantitative evaluation of the performance of a speech communication system.

There are three classes of variables involved in an articulation test: the personnel, talkers and listeners; the test materials, syllables, words, sentences, or continuous discourse; and the co111T1unication equipment, rooms, microphones, amplifiers, radios, earphones, etc. The present paper is directed toward the second of these classes of variables, the test materi­als. The central concern can be stated as follows: Why is a stimulus con­figuration, a word, heard correctly in one context and incorrectly in another?

Three kinds of contexts are explored:

(a) context supplies by the knowledge that the test item is one of a small vocabulary of items,

(b) context supplied by the items that precede or follow a given item in a word or sentence,

(c) context supplied by the knowledge that the item 1s a repetition of the immediately preceding item ..

All three kinds of context enable the listener to limit the range of alter .. natives from which he selects his response. The experimental problem varied the nature and amount of this contextual knowledge in order to study its influence upon perceptual accuracy. (author)

9. Beighley, K. C. An Experimental Study of the Effect of Four Speech Variables on Listener Comprehension. Speech Monographs, Vol. 19, pp. 249-258, 1952,

Workers in the field of speech have long been concerned with the rela­tionship of certain variables to comprehension of meaningful material. This experiment was designed to investigate the influence of four factors which might affect the comnunication of such material; (1) method of pre­sentation, whether oral or visual; (2) vocal skill of the reader in oral presentation; (3) difficulty of material presented; and (4) organization of material presented. (author)

10. Pollack, I. The Information of Elementary Auditory Dtsi:ilays~ Jour ... nal of the Acoustical Society of America, Vol, 25, p. 765, 1953.

Previous studies have shown that the amount of information transmitted with a simple one-d·1mensional auditory display is relatively small. This paper considers three conditions designed to increase the information transmission with elementary auditory displays. The three conditions or

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variables were (1) the frequency·range of tones investigated; (2) the uttlization of objective reference tones presented with the unknown tone; and (3) the 1•dimensionality" of.the display ... the number of independently varyi_ng stimulus aspects of the display. Little additional gain in infor­mation transmission is associated with the first factor; a moderate gain is associated with the second; and a relatively substantial gain 1s asso ... ci·ated with·the third. (author) ·

11. Pollack, l, and Ficks, L~ Information of Elementary Multidimensional Auditory Displays, Journal of the Acoustical Society of America, Vol. 26, p, 155, 1954.

The information transmission associated with elementary auditory dis .. plays conststing of a large number of independent stimulus aspects, e.g., the frequency or the sound level of a tone, was exami"ned. In general, multiple stimulus encoding is a satisfactory procedure for increasing the information transmission associated with elementary auditory displays. Further, extreme_subdivtsion of each stimulus aspect fails to produce sub­stanttal improvement tn the information.transmission. (author)

12~ Baddeley, A, D. Short ... Term Memory for Word Sequences as a Function of Acoustic, Semantic, and Formal Similarity. Quarterly Journal of Experimental Psychology, Vol. 18, pp. 362 .. 365, 1966.

Experiment I studies short-term memory (STM) for auditorily .. presented five-word sequences as a function of acoustic and semantic similarity. There ~s a large adverse effect of acoustic similarity on STM (72.5 per­cent) which was significantly greater (p<0,001) than the small (6.3 per­cent), but reliable effect (p<0.05) of semantic similarity.

Experiment II compared STM for sequences of words which had a similar letter structure (formal ·similarity), but were pronounced differently, with acoustically similar, but formally dissimilar words, and with control sequences, There was a significant effect of acoustic, but not of formal s imi 1 ari ty.

Experiment III replicated the acoustic similarity effect found in Experiment r using visual, instead of auditory presentation. Again, a large and significant effect of acoustic similarity was shown. (author)

13. Liberman, A. M., et. al. Perception of the Speech Code, Psychological Review, Vol. 74, pp, 431-461, 1967.

Man could not perceive speech well if each phoneme were cued by a unit sound. In fact, many phonemes are encoded so that a single acoustic cue carries information in parallel about successive phonemic segments. This reduces the rate at which discrete sounds must be perceived, but at the price of a complex relation between cue and phoneme: cues vary greatly

33

with context, and there are, in these: cases, no co111111utable acoustic seg ... ments of phonemic si:ze~ Phoneme perc~ption, therefore, requires a special decoder.. A possible model suppos~s that the encoding occ~rs below the level of' the (invariant) neuromotor commands to the articulatory muscles. The decoder may then identify phonemes by referring the incoming speech sounds to those commands. (author) ·

14. Murray, D. J, Articulation and Acoustic ConfusabilityfoShort,..Terrn Memory~ Journal of Experimental Psychology, Vol. 78, pp. 679~684, 1968.

Lists of letters varying in length and in acoustic confusability were presented for immediate probed recall, Presentation was either visual (with nonarticulation or silent articulation). It was found that recent visual items which were articulated gave acoustic confusability effects intermediate between the heavy effects obtained when retrieval was osten ... sibly from an auditory after .... echo and the negligible effects obtained when retrieval was ostensibly based on visual memory. These results sug­gest that arttculation enhances the discriminability, particularly of recent items in STM, and also that visual or auditory STM can be investi­gated independently of STM for speech .... coded information. (author)

15. Fell, J, c. and Laughery, K. R. Short-Term Memory: Mode of Presenta .. tion for~Alphanumeric Information. Human Factors, Vol. II, No. 4, pp, 401-406, 1969~ •

Perfonnance in a memory-span task using eight-letter sequences was explored as a function of presentation rate (.5, .75, 1,0, 2.0 1 and 3.0 sec/item) and presentation mode {visual, auditory, simultaneous visual and auditory, and mixed visual and auditory), Results indicate that per­formance in the mixed mode was inferior to the other three modes, but the other modes did not differ from each other. As presentation rate de­creased, performance improved, These results are consistent with current theories of memory and indicate that the mode in which alp:hanumeric infor­mation is displayed is unimportant, provided the modes are not mixed. (author) ·

16. McConnick, E. J, Human Factors Engineering, Thi'rd Edition McGraw-Hill Book Company, New York,· pp. 185-200, 1970.

This chapter discusses several variables to be evaluated in the use of auditory displays. A summary of the main points is as follows:

(a) In the use of auditory displays, the signal .. to-noise ratio is a more critical factor 1n detection of signals than signal inten-sity ts. · · ·

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(b) Auditory signals usually are more attention ... getti.ng than visual signals and, thus, lend themselves to use as warnt_ng signals.

(c) Audiowarning signals in some circumstances (such as for certain Air Force systems) need to perform three functions~ namely, attract attention, indicate the general nature of the emergency, and indicate the specific conditions, or suggest appropriate action. When the situation requires such a warning system, one signal component can perform the first two in combination, fol ... lowed by a second signal to perform the third funcUon.

(d) In the design of auditory displays, various principles can serve as guidelines where they are appropriate. Some of the most impor­tant are the following: compatibility (using signals that al ... ready have meaning for the purpose at hand), dissociability (dis­cerntbil i ty from any other ongoing audio input), forced entry (signal should be such that the receiver cannot ignore any aspect of it), and invartances (the same signal should designate the same information at all ttmes). ·

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l ' ! i

I l )

E. MASKING, LOUDNESS, AND AUDIO INTELLIGIBILITY .

1. Steinberg, J. C .. Effects of Distortion on the Recognition of Speech Sounds, Journal of the AcousticalSociety of America, Vol. 1, pp, 121-137, 1929,

The waves of speech sounds are characterized by three quantities, am-. plitude 2 frequency and phase, a11·three of which are essential to the cor­rect recognition of the sounds by an auditor. ln general, the term dis­tortion refers to relative changes in one or more of these quantities, in the process of transmitting the sound waves from speaker to auditor. Rec .. ognition ih the sense used here ref~rs to the correctness with which an audttor identifies the sound that he hears as being one, or some combina­tion of, the fundamental speech sounds, when ttfe combinations have no thought or meaning.

Distortion not only affects the recognizability of speech sounds, but the tonal character or naturalness of the sounds as well. The former aspect admtts of a quantitative determination by means of the so .. called articulation test, The latter aspect is considerably less definite and does not appear to be very stmply related, at least, to the recognizabi­lity, This paper is chiefly concerned with the effects of some of the more common types of distortion, and also the effects of the presence of extraneous sound waves, such as noise, upon the recognition of speech sounds. · (author)

2, Fletcher, H, and Munson, W, A. Relation Between Loudness and Masking, Journal of the Acoustical Society of A:"nerica, Voi. 9, pp, 1-10, 1937.

This paper discusses a quantitative relationship which has been between loudness and masking and which has enabled the development of a formula for calculating the loudness of sound. Although this formula seems to have general application to all types of sounds, it is particularly well-suited to the complicated types which approach a continuous spectrum. The method can also be applied to single frequency tones, or sounds having only a few components, but in these cases it is more difficult to obtain the masking audiogram accurately.

3, Egan, J. P; and Wiener, F. M. On the Intelligibility of Bands of Speech in Noise. Journal of the Acoustical Society of America, Vol. 18, pp. 435 .. 441, 1946 •.

Articulatton tests were cc>nducted with a large number of communication systems having band widths ranging from about one-half octave to a system covering the entire range of speech frequencies. The systems were·linear and their responses were approximately uniform over the pass band, with sharp cut .. offs at either end, The acoustic gain of the systems was expressed relative to the transmission of speech through one meter of air

36

between talker and-listener. Two spectra of masking noise were used, and each system was tested over a wide range of speech .. to-noise ratios. In one group of experiments the speech was filtered before mixi_ng with noise and in the other group both the speech and the noise were.passed through the same filter. For each of the band-pass systems, a relation between syllable articulation and level of received speech was obtained. From these gain functions, families of equal articulation contours may be derived. These contours show, for example, how the gain must be changed · for a given change in the band width of a system in order to maintain a constant articulation score~ (author)

4, French, N. R., and Steinberg, J, C. Factors Governing the Intelligi ... bility of Speech Sounds •. Journal of the Acousti'cal Society of America, Vol. 19, pp. 90~119, 1947.

The characteristics of speech, hearing, and noise are discussed in relation to the recognition of speech sounds by the ear. It is shown that the intelligibility of these sounds is related to a quantity called articu­lation index which can be computed from the intensities of speech and un­wanted sounds recei"ved by the ear, both as a function of frequency. Relationships developed for thts purpose are presented. Results calculated from these relations are compared with the results of tests of the subjec­tive effects on intelligibility of varying the intensity of the received speech, altering its normal intensity-frequency relations and adding noise. (author)

5, Miller, G. A. The Masking of Speech, PsychologiC:al Bulletin, Vol. 44, p. 105, 1947.

Knowledge of the ear~s susceptibility to interference is obviously a· matter of considerable practical value. Much .of our present knowledge has grown out of the job of developing the telephone, although research on speech"'conmunication problems in World War II has supplemented the earlier investigations. In the course of this research many different sounds were studied to determine the interference they might produce, and a review of the results shows the masking of speech to depend on three characteristics of the masking sound: (1). its intensity relative to the intensity of the

·speech, (2) its acoustic spectrum, and (3) its temporal continuity. A variety of .sounds are reviewed which are, or might be, encountered, and in every case the disruption of vocal conmunication is determined by these three attributes. Human speech is most seriously masked by an uni"nterrupted noise which has its power concentrated in the lower third of a spectrum covering the frequency-range from 100 to 4000 or 5000 cycles. (author)

6. Miller, G. A. and Licklider, c. R. The Intelligibility of Interrupted Speech. Journal of the Acoustical Society of America, Vol. 22, pp. 167 ... 173, 1950.

37

,.

This paper concerns the effects of interrupting speech waves - turning them on and off intermittently or masking them with intermittent noise -upon their intelligibility. The effects were studied with various rates of interruption and with the speech left undisturbed various percentages of the time. Tests were conducted (1) with speech turned on and off in quiet, (2) with continuous speech masked by interrupted white noise, and (3) with speech and noise interrupted alternately, the speech wave being turned on as the noise wave was turned off, and vice versa.

(1) When the speech wave is turned on and off infrequently, the per­centage of the message that is missed is approximately the same as the percentage of time the speech is off. When the interruptions are periodic and occur more often than 10,000 times per second, the interruptions do not interfere with the reception of the message. In the quiet it is easy to understand conversational speech so long as the interruptions occur more than 10 times per second.

(2) When continuous speech waves are masked by noise that is inter­rupted more than 200 times per second, intelligibility is independent of the i.nterrupti on frequency and of the percentage of time the noise is on, provided the ratio of average speech power to average noise power is held constant. Interrupted masking noise impairs intelligibility least tf the frequency of interruption is about 15 per second.

(3) When interrupted speech and interrupted noise alternate at fre­quencies below 10 alternations per second, the noise does not impair in­telligibility. At higher frequencies of alternation the temporal spread of masking becomes appreciable.

The general features of the resu1cs are approximately the same whether the interruptions occur periodically or at random. (author)

7. Egari, J. P. and Hake, H. W. On the Masking Pattern of a Simple Audi­tory Stimulus. Journal, of the Acoustical Society of America, Vol. 22, p. 622, 1950. . . .

. The masking audiogram of a pure tone is complicated by phenomena that arise from the interaction- of the test tone with the masking stimulus. The ·production of beats atid of different tones results in a masking audio­gram that does not represent the pattern of activity in the cochlea or nerve due to a simple masking stimulus. In the present experiments a narrow band of noise was used to mask pure tones. The "beat" heard in the i'!1"1edia~e vicinity of the masking noise is not prominent, and a test tone higher in frequency than the band of noise is detected in terms of the characteristic pitch of that tone rather than by means of a different tone.

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8. Garvey, W. D. The Intelligibility of Abbreviated Speech Patterns. Quarterly Journal of Speech, Vol. 39, pp. 296-306, 1953.

The extensive use of voice in present-day communications pointed to the importance of investigating the practical limits of speeded speech. This study was conducted at the University of Virginia, under contract with the United States Air Force, to determine the feasibility of speeding up speech in voice communications.

Earlier methods of speeding up recorded speech have lacked efficiency in that the intelligibility of the speech was substantially lowered by the distortion effects resulting from a frequency shift which accompanied the speed-up of the record. The analysis of the intelligibility of abbre­viated speech patterns presented in this study originated out of an effort to determine an efficient method for speeding up recorded speech. In these particular experiments portions of the speech pattern were removed by means of an electronic chopping switch.

9. Pickett, J. M. Effects of Vocal Force on the Intelligibility of Speech Sounds. Journal of the Acoustical Society of America, Vol. 38, pp. 902-905, 1956.

Measurements were made of the intelligibility of speech heard in noise and produced by different amounts of vocal force. Vocal force ranged from the weakest voiced whisper to a very heavy shout. The results show less than ffve percent deterior.ation in intelli~ibility over the range from a moderately low voice to a very loud voice (55 to 78 db in a free field at one m from the lips). Beyond these points intelligibility decreases abruptly and in a linear relation to decibel change in vocal intensity. Listener's errors are analyzed to determine the effects of the extremes of vocal force on the intelligibility of different parts of the syllable and of different vowels. (author)

10. Wathen-Dunn, W. and Lipke, D. W. On the Power Gained by Clipping Speech in the Audio Band. Journal of the Acoustical Society of America, Vol. 30, p. 36, 1958.

For more than .a decade it has been known, in a quatitative way, that the long-time average poser of a speech signal in an amplitude-limited communications system can be increased materially by clipping the peaks of the speech wave and amplifying the remainder until the new peaks have the maximum allowable amplitude. This power increase can be computed from the statistical distribution for the instantaneous amplitudes of speech. Some of the available distributions have been collected and compared, and upon their showing good agreement, one of.them has been used for the com­putation. Simple formulas show that the power increase can be neither greater than the amount of clipping, nor greater than the peak factor of speech. For 24 db of peak clipping, the power pain is about 12 db. The exact value depends upon the choice of peak factor for unclipped speech.

39

In practice, the actual gain in signal-to-noise ratio on peak-limited com­munications systems {e. g., AM and DSB radio) will be less than that com­puted here. {author).

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