AMRL-TR-67-119

;

THE EFFECTS OF HIGH INTENSITY NOISEtON HUMAN PERFORMANCE

I r RTANLEY HARIRIS, PhD

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II hiTR37?,1774-j u .JANUARY 1968Ju

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Distribution of this document is unlimited. Itmay be released to the Clearinghouse, Depart-ment of Commerce, for sale to the general public.

AEROSPACE MEDICAL RESEARCH LABORATORIESAEROSPACE MEDICAL DIVISIONAIR FORCE SYSTEMS COMMAND

WRIGHT-PATTERSON AIR FOICE BASE, OHIO

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- - NOTICES

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800 - May 1968 - C04SS - 34-707

AMRL-TR-67-119

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Foreword

This shdy was initiated by the Biomedical Laboratory, Aerospace MedicalResearch L ies, Aerospace Medical Division, Wright-Patterson Air ForceBase, Ohio 45433. The research was conducted by C. S. Harris, Biological Acous-tics Branch, Biodynamics and Bionics Divisio, under Project 7231, "Biomechawcsof Aerosice Operations," and Task 723103, "Biological Acoustics in AerospaceEnvironments." Acknowledgment is made of the assistance provided by Mr. H. C.Sommer and Staff Sergeant W. C. Knobloch of the Biomechanics ant. BionicsDivision. Research covered herein was accomplished in late 1906 and early 1967.

Mw technical report has been reviewed and is approved.

WAYNE IL McCANDLESSTechnical DirectorBiomedical LaboratoryAerospace Medical Research Labomtories

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AMRL TR-67-119 January 1968

ERRATA - May 1968

The following corrections apply to AMRL-TR-67-i 19, The Effects of

High Intensity Noise on Human Performance.

On page 10, Figures 7 and 8, the illustrations have beenreversed although the titles are printed correctly. The graph withabscissa "Noise Conditions" should be Figure 7, and the graph withabscissa "Sessions" should be Figure 8.

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Abst-rat

Four experiments were conducted on the effects of broadband, high intensitynoise on human performance. In two experiments the subjects pesrfmance wasmeasured on a D Task, based primarily upon visual discrizinationand short term memory, and in the other two experiments penfrmance wasmeasured on a Hand-Tool Dexterity Test. Four different noise exposure coodi-tions were used in each experiment: control (70dB), 12D dB. 130dB, and 140dB(re 0.0002 dyne/cm). In one experiment using the D Task, thesubjects wore earplugs, and in the oder, subjects wore earplugs and an emuffwith one earcup to produce an asymmetrical noise exposure at the ear Thesetwo types of ear protectors were worn also by the subjects in the two e3xeriments

using the Hand-Tool Dexterity Task. Decrements on the D Taskwere obiaed at the two highest noise intensities for w. aqMmtzical exp E ,_and no decrements were obtained for any symmetrical expomr W'th the hand-Tool Dexterity Test, significant decrements were obtained at the noe levels of130 dB and 140 dB with symmetrical exposure, and at 140 dB with the asym-mtrical exposure. The difference in performance between the two X-oups wasdue to a different initial level of ability on the task rather than due to syrmuetricalversus asymmetrical -posure conditions. The results indicate that asymmetricalexposure had a greamer detrimental effect on the D Task than thesymmetrical exposure, while there was no differential effet on the Hand-ToolDexterity Test These results are discussed as a possible effect of the actian ofhigh intensity noise on the vestibular system.

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SECTON LInur

Various sdmltv sylptom h bean m nmtd bt indivdual esposed to, N& ~Jet noise and several exhai she bemr Ifre to aixsinit for the SYnUeoin ?U=Mewnoosdizatiou and a genera weaknaess of the, body bave bumn suggested as due to vestimalsstimulto and to the elicitation of rd sb vilatiof the skn mxuscls:, and:t (rehs ,8)Symptom of M"na couui " disulky mntd~n hawe aso bee noted (ref 3).

In spite of the itr in Awlt of jet noise cc men working in such emkvizem vaylittle has heen awmplthe in the objective manasmrn of Il..an Iuwmao I ~ w imnoie. Any of the syncxris eeIme by individuals in jet noise could lead to a redactio n

wt Consciuousm e rfxfh 1, . 1 w cy could be dected rt seves*l at noisepneon e levels y. uthn wse nea-, to el2~icsutive rews f uct orte s t a

> Ition and mental aan~insinin previous suis(refs 4L 6). we have denowstated. that the ablity of su ieb behlam

an naw rails (equllilium function) Yas adversel afected at noise 1, R lev& elo ~w tlxatiat elicited the sei subjective syu~w discussed Awoe- A partisaauy - addim.in addition, to noise wa3y in prudnuing dersument cc the rai teag wa m asyrnetrimel Pres-enfttiof c thene to the ems, L e., him usa stimulation of wmeqmal itfifeS at* efc theanm. using hiOhW ofesite oise ctlw hmvetiaors harve fond aso eica inpm toproduce, mae evr sbjciv s than Vzomtica eposaes Wre 1).

Ile I stAndy Ewrw~ an exteosiom of the study just described. dt wausing the rail test. In this epewrt an afterpt was mode to I'duPuie wbetbes moambi

Rsut could be obA I -ed using Sig Im types Of tBask One tak was a Di - ~I I- TdAs thatrqIred primaril the w of visua Iueioito anmaht tarm mmoyand the Othff taok

was a Hared-Tool Dezt Test designed -- to memuae manipulative " kitadepwim ofintellectual fators (ref 2). 0f particular 1, 1u was the detuunatcA wlmer VSYintIcalarpt wrF has a maeadvers affect cnms tasks then symmoebrial exqpmoan r wbeIw &ae

o~jsmod cect is spe.o to the rai tesL~ The subjective mae used int fie nail tes stmdy(ref 4) wa also, used in the present exerata for 6orlto with dhe results oi the MeitTask and tl* HaindTol Dexterity Teds.

.1 I SECION IL

A total of 48 male univemRy s;dents was used as b in four esperinets. T uerepaid vo -,,tes and A we in teir late eOm K aly tunes. In aM€i to DmWaingat .imeLm. test Ae mnmcis frm 50D to M 4% IZ, soects bad jdmateJA aqu sen-tivity im both m fw ea& te hequecy. No s imcCed in the study ulb hadgrmef don 5 dB (re 0.O d,-o/cm) hearing difference betw the uigle and left ea at any

ftm1. -msoma hmng w SbiwoTdb wM Nmm&ad Dad*f To

HM SOURM AND C2MMNSubject were tested in a lap tevedmraic chiba (14.8 x 17.3 feet) ,,bh was vct

imp PIf the ePuP- eI. the suhjw the tLk, and the sound source Figure 1 w thelocaim of %e satiet and eViz in the oise wba e tle Hazd-Tool DekberityTest was being ad is ere. The subiect sat i a siedwm des wile td6ng the ape adPenil nDiu - 9.io Task.

FWgure 2 peems the azicut octave bamd leve of the me used m the study amd the ze-suting octav bend levels of te moise as a , c t e difuur types of er protectionprovided the subjects. Thwe wae tw baic map -e cadita IPse n"d to the ijetd.s asymtmwl pf a wditi in mUli the subjects uw= eusplap and so asyiranetical ex-pwn coodition in th~e s ,e arplgs in both em and an tzrcp theI ri estw.

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eac ci th m, mvAteae mm- bv up and~ to m& ~ie ==e, dc2 d~aa-

LUmdf "6d~ ci t12 boof the s!B*d utea fne tiat *4 reM 202E"' d

U, betwe fla par&cal bem z,~ the cme -enem abe-Ie =aiu msIi d-lmoa difil tbtoiGes oo wS si 93P the =bm-u ua c -AfbI c=95e~tm -A a 9dOf OXP.W the a*S~bet U-tG tD the MC3 Se CE Ei bMM t&W tO :l MM Tdiwwe comdo tot time aDattd tQ the tksi a expire&

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Pekrw m d& bA mw i tw -tm&~ eromw-bimmers

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Hand-Tool Dexterity TestThe equipment for this task consisted of three horizontal rows of nuts and bolts mounted

on a wooden stanchion. The nuts and bolts were of three different sizes and four of the same-.izes were mounted in each row. The Hand-Tool Dexterity Test was developed by Bennett "toprovide a measure of proficiency in using ordinary mechanics' tools" (ref 2). The subjects taskwas to remove all the bolts from the left upright and transer them to corresponding rows onthe right upright. The instructions and procedure recommended by Bennett (ref 2) were used.A foam rubber pad was placed over the working area surrounding the task to dampen the vibra-tion of the nuts and bolts produced by the high intensity noise. The score on this task was the

time taken by the subject to transfer the nuts and bolts from the left upright to the right upright.Although no norms for college students are presented by the author of this task, norms are p.,e-sented for 4 11 male adults at a vocational guidance center. The score corresponding to the 1stperentile was 12 min, 47 sec, to the 50th percentile 6 min, 53 sec, and to the 99th percentile4 min, 32 sec.

SUBJECTIVE MEASUREA sibjt.,,tive evaluation of the noise was obtained after each noise exposure. The measure

was based on a Semantic Differential technique developed by Osgood et al (ref 7) for measuringmeaning. The subjects were asked to rate "My Fxperience in the Noise Chamber" on 16 scales of"bipolar" adjectives. Four bipolar adjectives were chosen to assess each of four factors. Theadjective scales of good-bad, nice-awful, valuable-worthless, and pleasant-unpleasant were usedto assess an Evaluative factor (E). The scales of heavy-light, large-small, thick-thin, and strong-weak were used to assess a Potency factor (P). Sharp-dull, angular-rounded, active-passiv, andfast-slow were used to assess an Activity factor (A). The scales of awkward-graceful, private-

-calm, and constricted-spacious ere used to sample what Osgood et al (re 7)

uggest may represent "some sort of anxiety factor" (Anx). Standard instructions were given forthe Semantic Differential measure. Since in previous experiments these factors were significantlycorrelated and a more re!iable measure could be obtained by using one score ba.ed on all fourmeasures, in this study each subject's score was the mean of his ratings of the 16 bipolaradjectives. Scoring was on a scale from 1-7. A score of 1 would indicate that the subject ratedhis experience in the noise as good, light, passive, and calm, whereas a score of 7 would idi-cate that the subject rated his experience as bad, heavy, active, and excitable.

Our hypothesis was that the results obtained with the subjective measure would be similarto the results obtained in our previous study in which the subjective measure was presentedafter the rail test. In the rail test study, the mean subjective rating increased with the in-tensity -f the noise, and the means for the asymmetrical noise exposure conditions were higherthan the means for the symmetrical exposure conditions.

PROCEDURE AND EXPERIENTAL DESIGNUpon their first appearance at the laboratory subjects were given instructions and practice

in the proper procedure for performing the tasks. The groups that performed the DiscriminationTask came for two preliminary training sessions in which they performed the task without noisein the same manner as used in the experiment proper, i.e., two 4-minute testing periods separatedby a 1-minute rest period. In addition, at the end of the second preliminary training session sub-jects were briefly exposed to the noise at each of the intensity levels used in the study. Thegroups that performed the Hand-Tool Dexterity Test came for one preliminary training sessionin which they performed the test twice, and at the end of the practice testing were also exposed

to the noise at the intensity levels used in the study. Subjects were exposed to the noise duringI ,

the practice session to reduce possible anxiety that might arise later in the experiment due to the

naccustmed exposure to nois

The same experimental design was used in all experiments. Each subject received all ex-perimental conditions at ambient intensity noise levels of control (70 dB), 12D) dB, 130 dB, and140 dB (re 0.0002 dyne/cm2). The four experimental conditions were presented in lour differ-ent orders, ABCD, BDAC, CADB, and DCBA. Two subjects were assigned to each cf the ordersof presentation in the experiments with 8 subjects, and 4 were assigned for each order in theexperiments with 16 subjects. A summary of the experiments and the various conditions involved

in ea&h is give , in table I.

TABLE I

SUMMARY TABLE OF EXPERIMENTAL CONDITIONSExperi- No.of

me St Ear Protection Task During Noise After Noise

I 8 Earplugs Disc-rimination Task Rail* SubjectiveH 8 Earplugs and 1 Muff Discrimination Task Rail* Subjective

III 16 Earplugs Hand-Tool SubjectiveIV 16 Earplugs and I Muff Hand-Tool Subjective

*In the e im rag tert for erpedmaitus. an tion of thenoise, and the slbective evaluation ci the noise was obined sbuuat. reportedin aprevims paper (vet 4).

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SECTION III.Results

The same analysis of variance technique was applied to all data obtained in the experiments,since the same experimental design was used for all experiments. The technique was one recom-mended by Lindquist (ref 5), for use with a Type II experimental design.

Table II presents the results of Variance Analyses for the data obtained by use of theDiscrimination Task In the four analyses summarized in this table only one significant effectwas obtained for noise conditions. This effect was obtained for the first 4-minute testing sessionfor the asymmetrical exposure. Mean differences were evaluated by use of a t test. Thedecrements associated with this significant effect were obtained at 130 dB and 140 dB and theydiffered from the control measure at probability levels of p<.10 and p<.05 respectively (seetable III). Figure 4 presents these data in graphic form. Although, the absolute difference betweenany noise condition and the control condition is relatively small, the difference between asym-metrical and synmetrical exposures is clearcut for the first 4-minute period. There is improve-ment in performance, although not statistically significant, at the 130 dB and 140 dB levels inthe symmetrical group and a decrement in performance at these levels for the asymmetricalgroup. There was also a significant effect for sessions obtained during the first 4-minute testsession for the asymmetrical exposure. The meam of the 4th session was significantly larger thanthe means for sessions 1 and 2.

The results presented above were based on a corrected score measure which was the ntunberof boxes completed minus the number of errors made. Therefore, the decrement in performancecould have been due to an increase in the number of errors ordue to a decline in the number of

'io

00 SYUUIC*I.r&

CCtOM12ZO 130 140 Ito 130 1410IST4 .M 0 41.1

NOISE CWomows (48 rt 0.0002 Dyw/=2 )

Frgure 4. Me. C ed Sem f ine Cadhiam for A y 1mm 1• , Symmiv If, pms for 3.6 4-Mino PW

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InETAI'fw -3 mIS 4INto4

W8amswom ph

S. um m w WIU s -

twmam uSi se ft02Dimc2

rns. .Mm m~ auplAd rn Nim AuLi.fenAymulM

eadSy~ A pmqs snls 3h 4. s No u

A 04

NWCM A0,=I"ZRo .fib mh oW C W e wA " W a

*mm lii' w"Bo A~o

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items attempted. Figures 5 and 6 help to clarify what happened to the subjecs perfow n asa result of the noise exposures. In figure 5, during the first 4 minutes for the asymmetrical ez-posure, the subjects completed approximately the same number of boxes under all nee condi-tions. If the same period is examied in figure 6 fDr asymmetrical exposr the mean crm i-creased with the increasing intensity of the noise exposure. Therefore, the reamon for the decre-ment ir performance is obvious.

ITABLE HI f

RESULTS OF VARIANCE ANALYSES FOR CORRECFEDSCORE OF DISCRIMINATION TASK

Sme of Variance

Analysis Groups (Order) NoiseContickm Sessions NCzS

EurpugsandlI Muff

Ist 4 minutes us. p<.05 p<. 5 U.s.2n:14 minutes n.s. U.s. =. M.s

Ist 4 minu0 U.S. s. uL u.s2nd 4 minutes n.s. n.s. n.s. I.L

TABLE III

MEANS AND DIFFERENCES FOR COR RC'ED SCOREOF DISCRIMINATION TASK FOR NOISE CONDITIONS

Noise Condkttone Mean A B C D

-l ad l MuffIst4 Minutes

A (Cotro) 44.M .72 213 2z**B (IM dB) 45.00 2.88"* a0**C (130dB) 42.12 .12D (140dB) 42.00

Means for Nowilcaiit Meaa~resEarpls and1 Mu Control 120dB 130B 140db

2nd 4 Minutes 42.62 44.-75 4L00 43.42

1st 4 Minutes 45.00 44.5 45.88 450

2nd 4 Minutes 4.00 44.25 45.88 44.5*p<.10*P<.05

9' ILi _ ____ ___ ____ ___ ___ ____ ____ _Ia

344

aw

SES IOU30 14

Ag.., I. M. 1Ik, i Cmplat HmTm D@u Too 4* 3mvN&Cmdi.m for Aaymmkiad sd SmswI, smm

10I

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These figuares also make it obvious why no sign&f=at decrement in performance, was obtained- during the secondi 4 minutes for the asymmetrical exposure. As can be seen in igure 6, there is

little change in error scesm from the first 4 minutes to the second 4 mninutes however, figure 5reveals that the number of items completed, relative to the control group, increased with woiseintensity during the second 4-minute exposure and this increase cancelled out the effect of theerrors according to our scoring procedere. By examinin the same figures for symmetrical expos-ures. the mean error is much less ai the two higher noise levels than for the aymmetrical ex-

r- posures. Further, the small increase in error 13 more thau compensate for by an increase in thenumber of items attempted.I Table Al presents the results of tbe Analyses of Variance pesformed on the scoes obtitinedby use of the Hand-Tool Dexterity Test. la the analyses performed for the two etposure groupssignificant effects %wee obtained both for noise wnwtions and for sessions. Signifint increasesin the time taken to complete this task occurred at noise levels of IM0 dB and 140 dB foir sym-mtrc lx osure, a d t e ise ev l 10 B o smnet oues (se able V)

the task makes it difficult to determine, the relative elfects of asymmietrical vmus smmiexposure The difference between groups was due mainly to the dat obtained in sessou asI sen iu figare 8 where mean time to complete the task is p]ottcd against sessions: for both sym-metrical aid asymametrical exposure. There, was a large dierce between these gaop dur-

Because of the extremel poor performance of the subject during session I for asynunetrical ex-

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po ure regurdless of noise intensity level, differences between noise conditions were obscured.Pafonmmnce at the lower ncie levels was so poor that the subjects could not show much in-ease in mean prafrmance me, at the higher noise levels where an increase might be expected.

Ths vras indeed tho case as seen in fige 9 where the same data are pkwed as in figure 7 minusthe data for sesdon L With the i]at from sessin I removed, the shape of the curve for sym-

RESLTS OF VARIANCE ANALYSES FOR HAND-TOOL" DEXTERITY 1-EST (TIME SCORES)

Souce of VariceAnah, Groux(Order) NoieCorditiom Seniomu NC xS

EwphkW and 1 Muf n. p<.O05 p<.O01 n.s.a n . p<.1 p<.O01 ns.

TABLE V

MEANS AND MEAN DnFEBCE FOR NOISE CONDMONS FOR HAND-TOOLDMEEILT TEST (TIE SCORES IN SECONDS)

NoU CondaiNm Me= A B C D

E.wplgr m.d1 MuffA (Cadrol) 2 2.94 L81 17.00'B (12DdB) 2.19 4.75 14-,70C(130dB) 2L44 18.8D (140 db) 310M -

A(Qahol) 27M 7.13 13.69* 35.5B (1,0dB) 272M.5 9082 4238C(130db) 2938 2L86D(140db) 314.94

IPA

cuve for asy-munetrical expmure shows i .srge relative increase in the mean time to complete theU at the L0 dB Ievel This comparison brings the reslts of both groups into agreement an in-cresein the mean thme to comple the task at 130 dB and 10 dB over the mean time for con-trol and 1M d. The differenes a g notse lew are still larger r the symmetri xposuregroup thian for the asymmatil expome group and may represent a true difference betveen

in the experiment with the Hand-Tool Dexterity Test, three subjects mentioned that theywe bothered by the shaking of the smallest bolts in their stations by the noise at 140 dB. The

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shaking occurred when as part of the standardized test procedure the subjects transferred thesmallest nuts and bolts to the opposite side, tightened with the fingers, and then tightened furtherusing a screwdriver and an adjustable wrezwc. The mai difficulty occurred in getting the screw-driver and wrench in place after they had initially tightened the nuts and bolts with their fingerDirect observations by the experimenter indicated that shaking of the nuts and bolts did addto the time required to complete the task but only by a few seconds at most. Eleven subjects,questioned after the spontaneous comments of the other three had been received, reported thatthe shaking of the nuts and bolts bothered them very little and they thought it had little effecton their performance.

The Semantic Differential meane indicated that asymmetrical exposure was rated a wesevere subjecti'e experience than the symmetrical exposure condition when the Discrim ionTask was used. However, when the Hand-Tool Dexterity Task was used, there was little Aer-ence in the subjetv ratings -fo the symtia and asmetia grup (see table " andVU). In figure 10, there was a clear diffence between mean subjective ratings for the asym-

!4 "_ /STErTWAL ETO UtS K

3MLr I ITKO IT MT

WUKTRO IN0 130 ~40

metrica! and symmetri.cal exposures when the i tion Task was used. These data indicatetht this was the ca since a signifcant efect for noise conditiom was obtained in analym ofvariance for only the asymmetrical exposure. On the other hand, the symnmra exposur wouidse E l be more sevre at the higher noise lekils than asymnetical exposure for the Hand-T~oDexterity Test, if we judge from the curves in the figure. However, statistical analy3es c nduon these data indicate that this difference was probably not a genuine difference (see tables Vand VI) since for both groups the mean rating at 130 dB and 140 dB were both signican yhigher than the mean rating; at control and 120 dB, and the mean rating at 140 dB was signif-cantly greater than the mean rating at 130 dB.

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TABLE VI

RESULTS OF VARIAN.CE ANALYSES FOR SUBJECTIVE ItATNGS

source of VaniancACivjpk GM (Order) Nois Coniditiovs Sesim INC x S

Mental Task

Earplugs and 1 Muf ns. P<-005 U.S. U4.

Eeksnl. a-s. Da. US.

Hmi4-Tool Desfwg Te*Earplupand IMuff as. P<.001 n& us

Eapug s. p<M0 l aLS. US.

TABLE VUI

MANS AND MEAN DIFFEENCES FOR SUBJECTVE RATIN-GS A.T EACHNOMSE COMMITON IN ALL EXERMENTS

Noile cbmikDw Mem A BC D

Ding MemtW~A.Ewilug ad I Muf

A(Cbmtw4l 3.67 -24 mWB(M2dB) a.91 .15 IWO~C(I3OdB) 4.06D(l4OdB) 4,99

Mans -%r Nomns~ikanmMeasrEarplugs 3.60 3-71 3.84 4.31

During MmA-Tool Deeityv Test

Eaiplugs snd 1 MuffA(Comt1) 3.41 .10.46B (120dB) 3.51 Moo~C(1300B) 3A7 Me

*D(141)dBj 43

A(Clantro) 337325 L1B(l20dB) 3.9-60C(I3OdB) 3z~A3D (140 d8) 4m3

.P<-0 1

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E The reswits obtained mith the Di~a~Tas are realh* cearc~d if am1v the databmsd cm the cwxreaed 2 re w5mmdered- As)--riAmm xe posare had a efr~a -fedt cc Che task durinIg the Ews 4 minuts cf espo~e but wo dr-rimema effet during the secsxd44inuz~e mqr F, essicmi Fw!Smthe. syrzxnetriraI sxai s= We aDO effeck t cc=the Dum iTaskd~irring eiib the List c~seaxczd 4-gi3zmt psio

lhe results pmseted ab~ove %we base om .2 cocetd ste sne thet vu the v~bof hazes cnpietd Z CIZ he o~i f m =a&e Theme;. the dece in Df e~fcsmnccouid have beem dve to a= increwrn in the m~m of or~s a ecm in the nm~n3ci it o

atcipe.T~i- cierces bet.~ ary zuetrical and spnuetriai eqxswes can be =KilC-stood by c s2efing th Cz c iescIfdah ef Ply-, t tban thecorrected suem The most imsiz aspec is the dWrnoce -.mthe C=ba E1~ enmane bythe two groops- The asyirmebiW p- r -1 e at 130 dB and INDdB me only produced we uavsbut theina rmfcrthe secom4 4ewas al~mt s argas w sEx the M 4 m .Ulms was deaalv &-A the case f~b syimmetiical ezqs. The ofn1 emme -%z the latter cushome a clear iabu the EMs 4- pesiod to the second 4-nue petial.

11e appnras adqpaticm of the as~n.=ew-il to the - ccwrd by am nres iutbe nui i± amempted =d mot Ib a decrame im the =~ of =a& 1LeaatA*-timof c the sylmdeficl guzp to the mse mms due to a dern in the of~ bale at-

~~1 tunj~ ~~s, t t~ *a ebuuKm ine ccas i m 1 uemin uxtmst toite xes, s- iedc h ~znnto Task, the oeut f teMumm D=z-

s-vTas d& not -1 ust a difesveba! efc fm~ ---metrial %=s sT==xtica eqims Asgcaadecrcneaa in pesfammance, -a obtained =n the siiawetrics a weg t Od

and 14D dB. and! at 140 dB fmr the aryzzebical ezae Swap- flim rask w um mW-pnsug s~a knesim~s stmty msig a ragl 6W (teE 4).2 as as the D-; ink ITask i tds

The greatest d~mmm be the Hand-To Deasi Test &maps ocszd &ag msd1. uhm~ the as mmmetdcal ~es grax Wi Auh than the vsyuetica cq e Srot%The two gaup urn qufe arin perfamnaano 1me during the I&As these sesi111-A caly the daft of the ImA d the wese used to cicethemeamfur carxems(fi)e~fuas~nd th Il uve pmoizaethe a=-- he~m emtims

t ~ta!ida the bm wv of~ cm ta amd M~ J&. flbmrx we 'would tem.eL% flatif subjects ci compaaC inkiai aliliy had bm ed a a iceas in :-he timet~i to,

cupeethe tas w%=d bave rcue at the hgE%4as ± imA les for 1c6 sywmdicaland aszzruical P

71ee wre a zri~CE posbe rets for the biwc tD demastrte, a diffal d~eEu ~ ~ ~ ~ ~~~M aAw ia-aacl~ s ~ POiSSUily is tint the adverle efte cmpefin

for both asiuMnui arid Symmetuicals was due to a P! -, =veczics3 1 Sp p mxw!th tils Uask and this hnia itfeece, Was sLa e to c Pe a cffrnWa efe Asmenfimed in the -1, 1s sctionk, the sub~jects sta2tec. thedxy urn bctd by sbdiag ci tlesuzaLest bus in fbetkm at the !%%we ktacziy kev] of 140D d&L Machania. imr-

fimow m~mtedy do-wn 1mm JR Acs -. cw thoce- a subjects tepcxislthi !=-x f hebksaed os3aw dim dm-- very ft- Houe-- btrCeo

if puib*y did not r F ie he &ammea at IM aM.

La5

< Considleing the dat obtained in previous studies on the rail task, and in the present stuydyon the Discrimination Task and the Hand-Tool Dexterity Task, the more adverse effects may be ex-

pected with asymmetrical exposure on tasks that require a high degree of control over bodilybalance and tAslx that require visual discrimination and short term memory. However, on simplemanual dexterity tasks there woul seem to be little difference in the effects of asymmetricalversus symmetrical exposurm Additional exermnts should be conducted using subjects withtesame initial ability on manure1 dexterity tasks to determine the influence of this variable.

The overall results seem clear in pointing out that the rated severity of noise exposure isvery much affected by the activity an individual is engaged in when presented the noise. Thedata obtained by use of the subjective measure agree well with t&e results of the rail test and theDiscrimination Task in that asymmetrical exposures were rated as being more severe than sym-metrical exposures. In addition, if the difference on the HAnd-Tool Dexterity Test was due to thedifference in the initial level of ability of the groups on this task rather than to the symmetrical-asymmetrical variable, then the subjective measure also agrees with the results of this task, sincesubjective ratings indicate essentially no difference !n results as a consequence of symmetry-asymmety.

The results of the present study and the previous one using the rail test are imusually deer-cut since most of the literature on the effects of noise on human performance point out the con-fused state of the area. Shoenberger and Harris (ref 9) state- "Perhaps the only conclusion onecan reach from reading rciews of the effects of noise on human performance is that there areeffects. Whether these effects are detrimental or facilitative (or both), how they are related tointensity, what changes occur over time, etc, remain largely undetermined." The main reason ourresult: seem clearcut relative to the previous literature is that we are no longer studying the sameproblem as is discussed in some of the early review articles on the effects of noise on performance.Although the noise intensities in the ear canals of our subjects were no higher than have beenused in many previous experiments reported in the literature, the difference appears to be greaterextra-auditory effects of noise on ether body mechanisms in the present studies. The exact extra-auditory system that interacts with noise in the ear canal to produce decrements in performanceis not known at this time. Ades (ref 1) has suggested a number of years ago that "the first sensorysystem after the auditory to be assaulted by intense noise is the vestibular." Our results give somesupport to this premise since those tsts that involved greater proprioceptive activity (the railtest and Hand-Tool Dexterity Test) revealed greater sensitivity to the noise than did the test

Ithat involved little proprioceptive act- "'- (Discrimination Task). Many other explanations of theresults of the preesnt experiment could be offered, however additional research is needed to bet-ter define the response of the vestibular system to high intensity noise exposure.

I 16IA

RIP- -~= ---------- ______

References1. Ades, H. W., "Orientation in Space," Benox Report: An Exploratory Study of the Biological2. Effects of Noise, ONR Project NR 144079, The University of Chicago, December 1953.

2. Bennett, G. K., Manual of Directions for the Hand-Tool Dexterity Test, New York: The Pay-chelogical Corporation. No date given.

3. Dickson, E. D. D., Chadwick, D. L., "Observations on Disturbances of Equilibrium and OtherSymptoms Induced by Jet-Engine Noise," ). Laryngol. and OtoL, 65:154-165, 1951.

4. Harris, C. S., von Cierke, H. E., "The Effects of High Intensity Noise on Human Equilibrium,"E Paper presented at Annual Convention of Aerospace Medical Association, Washington, D. C.,

April 1967.&5. Lindquist, E. F., Design and Analysis of Experiments in Psychology and Education, Houghton

Mifflin Company, Boston, 1953.

6. Nixon, C. W., Harris, C. S. and von Gierke, H. E., Rail Test to Evaluate Equilibrium in Lou;-Level Wideband Noise, AMRL-TR-66-85 (AD 613315), Aerospace Medical lteseareh Labora-tories, Wright-Patterson AFB, Ohio, July 1966.

7. Osgood, C. E., Suci, G. J., and Tannenbaum, P. H., The Measurement of Meaning, Universityof Illinois Press, Urbana, 1957.

8. Parrack, H. 0., Eldredge, D. H., and Koster, H. F., Physiological Effts of Intense Sound,Memo. Report No. MCREXD-695-71B, U. S. Air Force, Air Material Command, Wright-Pat-terson AFB, Ohio, May 1948.

9. Shoenberger, R. W., Harris, C. S., 'Human Performance as a Function of Changes in AcousticNoise Levels," 1. Engineering Psychology, 4, 108-119.

35

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DOCUMENT CONTROL DATA -R & D,Security classiliction of title, body of abstract or I Indexing annotation must be entered when the overall report I clssified)

1. ORIGONATING ACTIVITY (Corporal* author) 1a. REPORT $ECURIT. CLASSIFICATION

Aer.space Medical Research Laboratories UNCLASSIFIEDAerospace Medical Div., Air Force Systems Command 2b. GROUP

'Wright-Patterson AFB, Ohio 45433 N/A1. IREPORT TITLE.I

THE EFFECTS OF HIGH INTENSITY NOISE ON HUMAN PERFORMANCE

. CESCRIPTIVE NOTES (pe ofreport end Inclu.lve date)

Final Report, October 1966 - January 1967L= I1. AUTHORISI (First nxte, middle Initial, lat name)

C. Stanley Harris, PhD

6 REPORT DATE 78. TOTAL NO. OF PAGES 7b. NO. OF RFSJanuary 1968 17 9

94. CONTRACT 04 GRANT NO. 9a. ORIGINATOR*S REPORT NUMBER(S)

b. RoJECTNo. 7231 AMRL-TR-67-119

Task No. 723103 9b. OTHER REPORT NO(S) (Any other num.rb. hat may be C..j.nod

,0. I,..vo . .. I1.DISTRISUTtON STATEMENT

Distribution of this document is unlimited. It may be released to the Clearinghouse,

Department of Commerce, for sale to the general public.

It. SUPPLEMENTARY NOTES 12. SPONSORING M:LITARY ACTIVITY

Aerospace Medical Research LaboratoriesAerospace Medical Div., Air Force Systems

___Command, Wright-Patterson AFB, OH 45433IS* AISSTRACT

Four experiments were conducted on the effects of broadband, high intensity noise onhuman performance. In two experiments the subjects' performance was measured on aDiscrimination Task, based primarily upon visual discrimination and short term memory,and in the other two experiments performance was measured on a Hand-Tool DexterityTest. Four different noise exposure conditions were used in each experiment: control

(70 dB), 120 dB, 130 dB, and 140 dB (re 0.0002 dynecu)In one experiment using the

Discrimination Task, the subjects wore earplugs, and in the onher, subjects wore ear-

plugs and an earmuff with one earcup to produce an asymmetrical noise exposure at thep sdears. These two types of ear protectors were woan also by the subjects in the twoexperiments using the Hand-Tool Dexterity Task. Decrements on the DiscriminationTask were obtained at the to highest noise intensities for the asymmetrical exposure,and no decrements were obtained or any symmetrical exposure. With the Hand-Tool

Dexterity Test, significant decrements were obtained at the noise levels of 130 dB and140 dB with symmetrical exposure, and at 14 dB with the asymmetrical exposure. Thedifference in performance between the two groups was due to a different initia level of

ability on the task rather than due to symmetrical versus asymmetrical exposureconditions. The results indicate that asymmetrical exposure had a greater det-imentaleffect on the Discriminacion Task than the symmetrical exposure, while there was nodifferential effe,,t on the Hand-tool Dext erity Test. These results are discussed as apossible effect-of the action o o high intensity noise on the vestibular system.

DD INO,.v1473

Securty Classification

Security Classification

14 ~~~KEY WORDS ALN HK

ROLE WT ROLE WI ROLE WT

High Intensity NoiseI

Motor PerformanceMental PerformanceEquilibrium

ONScrtrla~fCUf