spotlighting the audio

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AUDIO SPOTLIGHTING

A SEMINAR REPORT

Submittedin partial fulfillmentoftherequirementsfortheaward of degree of

BACHELOROF TECHNOLOGY

inELECTRICAL AND ELECTRONICS ENGINEERING

by

WINSTON NETTO (SEE 1697)

SCMS SCHOOL OF ENGINEERING & TECHNOLOGY

(Affiliated to M.G University)VIDYA NAGAR, PALISSERY, KARUKUTTYERNAKULAM-683 582

JULY 2009


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CERTIFICATE

This is to certify that the seminar work entitled

AUDIO SPOTLIGHTING

was presented by WINSTON NET TO SEE - 1697 of the Seventh

semesterElectrical and Electronics Engineering inpartial fulfil lmentof the

requirementfortheaward of B achelo r of Techno logy Degree in Ele ctrical and

Electronics Engineering under Mahatma Gandhi University during the

year 2009 2010 under my guidance at SCMS School of Engineering and

Techno logy , Karukutty.

Head of DepartmentFaculty in Charge Electrical and Electronics Engineering


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ACKNOWLEDGEMENT

It is with great enthusiasm and learning spirit that I bring out this seminar

report. I also feel that its the right opportunity to acknowledge the support and

guidance that came in for various quarters during the course of completion of

my seminar.

I express my gratitude to Head of Department (EEE) for rendering me all

facilities and guiding me right through the end for the successful completion of

the work.

I express my gratitude to CHRISMOL PAUL, Grade-I Lecturer, EEE

department for guiding me right through the end for the successful completion

of the seminar.

I am also obliged to the faculty of Electrical and Electronics Department, for

giving me their timely suggestions in my venture. Above all I express my

thanks to Almighty for the blessings showered on me which leads to the

successful completion of this work. Despite the best efforts put in by me, it is

possible that some unintentional errors might have eluded me. I shall

acknowledge with any such errors if pointed out.


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A B STRACT

Audio spot lighting is a very recent technology that creates focused beams of sound similar

to light beams coming out of a flashlight. By shining sound to one location, specific

listeners can be targeted with sound without others nearby hearing it. It uses a non-linear

acoustics for its working. But it is real and is better than any conventional loud speaker.

This acoustic device comprises a speaker that fires inaudible ultrasound pulses with very

small wavelength which act in a manner very similar to that of a narrow column. The ultra

sound beam acts as an airborne speaker. Holosonic Research Labs invented the Audio

Spotlight that is made of a sound processor, an amplifier and the transducer. This use

ultrasound based solutions to beam sound into a focused beam. Audio spotlight can be

either directed at a particular listener or to a point where it is reflected. The targeted or

directed audio technology is going to a attain a huge commercial market in entertainment

and consumer electronics and technology. Being the most recent and dramatic change in the

way we perceive sound, audio spot light technology can do many miracles in various fields

like, Home theatre audio system, Navy and military applications, museum displays etc.

Thus audio spotlighting helps us to control where sound comes from and where it goes.


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IND EX

SL NO. CONTENTS PAGE NO.

1 INTRODUCTION 1

2 THEORY 2

3 TECHNOLOGY OVERVIEW 3

4 RANGE OF HEARING 5

5 WORKING 6

6 BEAM DISPERSION 9

7 ARCHITECTURE 10

8 MODES OF LISTENING 13

9 ADVANTAGES 14

10 APPLICATIONS 15

11 FUTURE OF AUDIO SPOTLIGHTING 17

12 CONCLUSION 18

13 REFERENCE 19


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L IS T O F FIGURES

FIGURE NO. FIGURE NAME PAGE NO.

1 PROPAGATION OF SOUND BEAM 2

2 CONVENTIONAL SPEAKERS 4

3 AUDIO SPOTLIGHTING SPEAKERS 4

4 RANGE OF HEARING 5

5 AUDIO SPOTLIGHTING EMITTER 6

6 DIRECTIVITY 7

7 COMPUTER SIMULATION OF SOUND BEAM 9

8 DISPERSION OF SOUND BEAM 11

9 BLOCK DIAGRAM 10

10 PARAMETRIC LOUDSPEAKER 12

11 DIRECTE C AND PROJECTE D AUD IO 13


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INTRODU CTION

Hi-fi speakers range from piezoelectric tweeters to various kinds of mid-range

speakersand woofers which generally rely on circuits ant large enclosures to produce

quality sound, whether it dynamic, electrostatic or some other transducer - based

design.Engineershave struggled fornearly a century toproducea speakerdesignwith

the ideal

2OHz - 2O,OOOHz capability of human hearing and also produce a narrow beamof

audiblesound.

Audio spot lighting is a very recent technology that creates focused beams of sound

similar to light beams coming out of a flash light. Specific listeners can be targeted

withsound without others nearby hearing it, i.e. to focus the sound into a coherent and

highly directional beam.Itmakesuseofnon-linearityproperty ofair.

The Audio spotlight developed by American Technology Corporation uses ultrasonic

energy to create extremely narrow beams of sound that behaves like beam of light. Audio

spotlight exploits the property of non-linearity of air. A device known as parametric

array employs the non-linearity of the air to create audible by products from

inaudibleultrasound, resulting in extremely directive and beam like sound. This

source canprojected about an area much like a spotlight and creates an actual

specialized sounddistant from a transducer. The ultrasound column acts as a airborne

speaker, and as thebeam moves through the air gradual distortion takes place in a

predictable way. Thisgives rise to audible components that can be accurately

predicted and precisely controlled.


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T H EORY

The regular loudspeakers produce audible sound by directly moving the air molecules.

The audible portions of sound tend to spread out in all directions from the point of

origin. They do not travel as narrow beams. In fact the beam angle of audible sound is

very wide, just about 360 degrees. This effectively means that the sound you hear will be

propagated through the air equally in all directions. Convent ional loudspeakers suffer

from amplitude distortions, harmonic distortion, inter - modulation distortion, phase

distortion, crossover distortion, cone resonance etc. Some aspects of their mechanical

aspects are mass, magnetic structure, enclosure design and cone construction.

In order to focus sound into a narrow beam, you need to maintain a low beam angle that

is dictated by wavelength. The smaller the wavelength, less the beam angle and hence,

the more focused the sound. The beam angle also depends on the aperture size of the

speaker. A large loudspeaker will focus the sound over a smaller area. If the source

loudspeaker can be made several times bigger than the wavelength of the sound

transmitted, then a finely focused beam can be created. The problem here is that this is

not a very practical solution, thus the low beam angle can be achieved only by making

the wavelength smaller and this can be achieved by making use of ultrasonic sound.

F I G 1 : F.JOSEPH POMPEI AT T HE M IT L A B . PROPAGATION OF S OUND BEAM

F ROM AUD IO SPOTLIGHTING DEVIC E.


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T ECH NOLOGY OVE RVIEW

The technique of using a nonlinear interaction of high - frequency waves to generate low

- frequency waves was originally pioneered by researchers developing underwater sonar

techniques in 1960's. In 1975, an article cited the nonlinear effects occurring in air. Over

the next two decades, several large companies including Panasonic and Ricoh attempted

to develop a loudspeaker using this principle. They were successful in producing some

sort of sound but with higher level of distortion (>50%). In 1990s, Woody Norris a

Radar Technician solved the parametric problems of this technology.

Audio spotlighting works by emitting harmless high frequency ultrasonic tones that

human hear cannot hear. It uses ultrasonic energy to create extremely narrow beams of

sound that behave like beams of light. Ultrasonic sound is that sound which have very

small wavelength - in the millimeter range. These tones make use of non-linearity

property of air to produce new tones that are within the range of human hearing which

results in audible sound. The sound is created indirectly in air by down converting the

ultrasonic energy into the frequency spectrum we can hear.

In an audio spotlighting sound system there are no voice coils, cones or enclosures. The

result is 'sound with a potential purity and fidelity which we attained neverbefore'.

Sound quality is no longer tied to speaker size. This sound system holds the promise of

replacing convent ional speakers in homes, movie theaters and automobile - everywhere.


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F I G 2: CONVENTIONAL SPEAKERS

F I G 3: A UDIO SPOTLIGHTING


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RANGE OF H EARING

The human ear is sensitive to frequencies ranging from 20 Hz to 20,000 Hz. If the range

of human hearing is expressed as a percentage of shift from the lowest audible frequency

to the highest it spans a range of 100,000 percent. No single loudspeaker element can

operate efficiently over such a wide range offrequencies.

Using this technology it is possible to design a perfect transducer which can work over a

wide range of frequency which is audible to human hear.

F I G 4: R A N G E OF HEARING


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W ORKING

The original low frequency sound wave such as human speech or a music is applied into

an audio spotlight emitter device. This low frequency signal is frequency modulated with

ultrasonic frequencies ranging from 21 kHz to 28 kHz. The output of the modulator will

be the modulated form of original sound wave. Since ultrasonic frequency is used the

wavelength of the combined signal will be in the order of few millimeters. Since the

wavelength is smaller the beam angle will be around 3 degree, as a result the sound beam

will be a narrow one with a small dispersion.

F I G 5: AUDIO SPOTLIGHTING EMITTER


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While the frequency modulated signal travels through the air, the nonlinearity property

of air comes into action which slightly changes the sound wave. If there is a change in a

sound wave, new sounds are formed within the wave. Therefore if we know how the air

affects the sound waves, we can predict exactly what new frequencies (sounds) will be

added into the sound wave by the air itself. The new sound signal generated within the

ultrasonic sound wave will be corresponding to the original information signal with a

frequency in the range of 20 Hz to 20 kHz will be produced within the ultrasonic sound

wave. Since we cannot hear the ultrasonic sound wave we only hear the new sounds that

are formed by non - linear action of the air. Thus in an audio spotlighting there are no

actual speakers that produces the sound but the ultrasonic envelope acts as the airborne

speaker.

F I G 6: DIRECTIVITY


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The new sound produced virtually has no distortions associated with it and faithful

reproduction of sound is freed from bulky enclosures. There are no woofers or

crossovers. This technology is similar in that you can direct the ultrasonic emitter

towards a hard surface, a wall for instance and the listener perceives the sound as coming

from the spot on the wall. The listener does not perceive the sound as emanating from

the face of the transducer, but only form the reflection of the wall. For the maximum

volume (sound level) that trade show use demands, it is recommended that the Audio

Spotlight speaker, more accurately called a transducer, is mounted no more than 3 meters

from the average listeners ears, or 5 meters in the air. The mounting hardware is constructed

with a ball joint so that the Audio Spotlights are easily aimed wherever the sound is desired.

F I G 7: COMPUTER SIMULATION OF S O U ND BEAM


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B E A M DISPERSION

F I G 8: DISPERSION OF S OUND BEAM

Figure shows the dispersion of sound beam from an audio spotlighting emitter. Even

after traveling a distance of 10m the beam covers only an area of 3.2 meter square.


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COMPONENTS OF AUDIO SPOTLIGHTING SYSTEM

1. Power Supply.

2. Frequency oscillator.

3. Modulator.

4. Audio signal processor.

5. Microcontroller.

6. Ultrasonic amplifier.

7. Transducer.

F I G 9: BL OCK DIAG R AM OF AN A U DIO SPOLIGHTING SYSTEM


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1. Power Supply: Like all electronic systems, the audio spotlighting system works off

DC voltage. Ultrasonic amplifier requires 48V DC supply for its working and low

voltage formicrocontrollerunit and other process management.

2. F r e q u e n c y oscillator: The frequency oscillator generates ultrasonic frequency

signals in the range of (21,000 Hz to 28,000 Hz) which is required for the

modulat ion ofinformation signals.

3. M o d ul a t o r : In order to convert the source signal material into ultrasonic signal a

modulat ion scheme is required which is achieved through a modulator. In addition,

error correction is needed to reduce distortion without loss of efficiency. By using a

DSB modulatorthe modulation index can be reduced to decrease distortion.

4. Au d i o s ign a l processor: The audio signal is sent to electronic signal processor

circuit where equalization and distortion control are performed in order to produce

a good quality sound signal.

5. M i c r o c on tr oll e r : A dedicated microcontroller circuit takes care of the functional

management of the system. In the future version, it is expected that the whole

process like functional management, signal processing, double side band

modulat ion and even switch mode power supply would be effectively taken care of

by a single embedded IC.

6. Ultrasonic Amplifi er: High - efficiency ultrasonic power amplifiers amplifies the

frequency modulated wave in order to match the impedance of the integrated

transducers. So that the output of the emitter will be more powerful and can cover

more distance.


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7. T r a n s d u c e r : It is 1.27 cm thick and 17" in diameter. It is capable ofproducing

audibility up to 200 meters with better clarity of sound. It has the ability of real time

sound reproduction with zero lag. It can be wall, overhead or flush mounted. These

transducers are arranged in form of an array called parametric array in order to

propagate the ultrasonic signals from the emitter and thereby to exploit the nonlinearity

property of air.

F I G 10: PARAMETRIC LOUD SPEAKER


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MODES OF LISTENING

There are two modes oflistening:

1. Direct Mode.

2. Projected Mode.

F I G 11: DIRECTED A UDIO AND PROJECTED AUDIO

Di r e c t M o d e: Direct mode requires a clear line of approach from the sound system unit

to the point where the listener can hear the audio. To restrict the audio in a specific area

this method is appropriate.

Proj ected or Virtual mode: This mode requires an unbroken line of approach from the

emitter of audio spotlighting system, so the emitter is pointed at the spot where the is to

be heard. For this mode of operation the sound beam from an emitter is made to reflect

from a reflecting surface such as a wall surface or a diffuser surface. A virtual sound

source creates an illusion of sound source that emanates from a surface or direction

where no physical loudspeaker ispresent.


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ADVANTAGES

1. Can focus sound only at the place you want.

2. Ultrasonic emitter devices are thin and flat and do not require a mounting cabinet.

3. The focused or directed sound travels much faster in a straight line than conventional

loudspeakers.

4. Dispersion can be controlled - very narrow or wider to cover more listening area.

5. Can reduce or eliminate the feedback from microphones.6. Highly cost effective as the maintenance required is less as compared to conventional

loud speakers and have longer life span.

7. Requires only same power as required for regular speakers.

8. There is no lag in reproducing the sound.


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APPLICATIONS

1. Au t o mo b il e s : Beam alert signals can be directly propagated from an

announce ment device in the dashboard to the driver. Presently Mercedes - Benz

buses are fitted with audio spotlighting speakers so that individual travellers can

enjoy the music of there on interest.

2. R e t a il s a le s : Provide targeted advertising directly at the point ofpurchase.

3. S a f e t y o ff i c ia ls : Portable audio spotlighting devices for communicating with a

specific person in a crowd ofpeople.

4. P u b li c announcement : Highly focused announcementin noisy environments such

as subways, airports, amusementparks, traffic intersections etc.


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5. E m e r g e n c y r e s c ue. Rescuers can communicate with endangered people far from

reach.

6. Entertainment s y s t e m : In home theatre system rear speakers can be eliminated by

the implementation of audio spotlighting and the properties of sound can be

improved.

7. M u s e u m s : In museums audio spotlight can be used to describe about a particular

object to a person standing in front it, so that the other person standing in front of

another object will not be able to hear the description.

8. M il it a r y a p p li c a t ion s . Ship - to - ship communications and shipboard

announcements.

9. Audio/Video conferencing. Project the audio from a conference in four different

languages, forma single central device without the need forheadphones.

10. S o u n d bu ll e ts : Jack the sound level 50 times the human threshold of pain, and an

offshoot of audio spotlighting sound technology becomes a non-lethal weapon


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FU T UR E OF A UD I O SPOTLIGHTING

Even the best loudspeakers are subject to distortion and their omni directional sound is

annoying to the people in the vicinity who do no wish to listen.

Audio spotlighting system holds the promise of replacing convent ional speakers. It

allows the user to control the direction ofpropagation of sound. The audio spotlight will

force people to rethink their relationship with sound. Audio spotlighting really "put

sound where you want it".


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C ONCLUSION

Audio spotlighting is real ly go ing to make a revolution in sound

transmission and the user can decide the path in which audio signal should

propagate. Due to the unidirectional propagation it finds application in

large number of fields.Audio spotlighting system is go ing to shape the future

ofsound and will serveourears with magicalexp erien ce.


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R EFE R ENCE

1. F. Joseph Pompei. The use of airborne ultrasonics for generating audible sound beams.

Journal of the Audio Engineering Society, P. J. Westervelt. Parametric acoustic array.

Journal of the Acoustical Society of America.

2. Thomas D. Kite, John T. Post, and Mark F. Hamilton. Parametric array in air: Distortion

reduction by preprocessing. Journal of the Acoustical Society of America.

3. Jacqueline Naze Tjotta and Sigve Tjotta. Nonlinear interaction of two collinear,

spherically spreading sound beams.

4. www.sil e ntsound.c o.z a Silent sound

5. www.wikip e di a .o r g - Sound from Ultrasound

6. www.techalone.com - Audio spotlighting

7. www.howstu ff w o r ks.c o m

8. www.holosonics.com

9. Electronics For You - Vol. 40 January 2008
http://www.silentsound.co.za/http://www.silentsound.co.za/http://www.silentsound.co.za/http://www.wikipedia.org/http://www.techalone.com/http://www.howstuffworks.com/http://www.howstuffworks.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.holosonics.com/http://www.wikipedia.org/http://www.techalone.com/http://www.howstuffworks.com/http://www.holosonics.com/http://www.silentsound.co.za/

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