audio spotlighting by bharadwaj

8/3/2019 Audio Spotlighting by Bharadwaj

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By B. Bharadwaj

&

B. Shiva Ram



y Engineers have struggled for nearly a century to produce aspeaker design with the ideal 20Hz - 20,000Hz capabilityof human hearing and also produce a narrow beam ofaudible sound. Audio spot lighting is a very recent

technology that creates focused beams of soundsimilar to light beams coming out of a flash light.Specific listeners can be targeted with sound withoutothers nearby hearing it, i.e. to focus the sound into acoherent and highly directional beam. It makes use of non-

linearity property of air. A device known as parametricarray employs the non-linearity of the air to createaudible by products from inaudible ultrasound, resultingin extremely directive and beam like sound.



y T he technique of using a nonlinearinteraction of high - frequencywaves to generate low -frequency waves was originally

pioneered by researchersdeveloping underwater sonartechniques in 1960's. Audiospotlighting works by emittingharmless high frequency

ultrasonic tones that human hearcannot hear. It uses ultrasonicenergy to create extremelynarrow beams of sound thatbehave like beams of light.



y T hese tones make useof non-linearityproperty of air toproduce new tones thatare within the range ofhuman hearing whichresults in audible sound.T his sound systemholds the promise ofreplacing conventional

speakers in homes,movie theaters andautomobile -everywhere.



y T he human ear is sensitive tofrequencies ranging from 20 Hz to20,000 Hz. If the range of humanhearing is expressed as apercentage of shift from the

lowest audible frequency to thehighest it spans a range of100,000 percent. No singleloudspeaker element can operateefficiently over such a wide rangeof frequencies. Using this

technology it is possible to designa perfect transducer which canwork over a wide range offrequency which is audible tohuman hear.



y T he original low frequency sound wave such as human speech or amusic is applied into an audio spotlight emitter device. T his lowfrequency signal is frequency modulated with ultrasonicfrequencies ranging from 21 kHz to 28 kHz. T he output of themodulator will be the modulated form of original sound wave.

Since ultrasonic frequency is used the wavelength of thecombined signal will be in the order of few millimeters. Since thewavelength is smaller the beam angle will be around 3 degree, asa result the sound beam will be a narrow one with a smalldispersion.



y If there is a change in a sound wave, new sounds are formedwithin the wave. T he new sound signal generated within theultrasonic sound wave will be corresponding to the originalinformation signal with a frequency in the range of 20 Hz to 20kHz will be produced within the sound wave. Since we cannot

hear the ultrasonic sound wave we only hear the new sounds thatare formed by non - linear action of the air. T hus in an audiospotlighting there are no actual speakers that produces thesound but the ultrasonic envelope acts as the airborne speaker.



y T he new sound produced virtually has no distortionsassociated with it. T here are no woofers or crossovers.T his technology is similar in that you can direct theultrasonic emitter towards a hard surface, the listener

perceives the sound as coming from the spot on the wall. Itis recommended that the Audio Spotlight speaker, moreaccurately called a transducer, is mounted no more than 3meters from the average listeners ears, or 5 meters in theair.



y Figure shows the dispersion of sound beam from an audiospotlighting emitter. Even after traveling a distance of10m the beam covers only an area of 3.2 meter square.



(Power Supply.

(Frequency oscillator.

(Modulator.

(Audio signal processor.

(Microcontroller.

(Ultrasonic amplifier.

(T ransducer.

PARAMETRIC LOUD SPEAKER



(Direct Mode

(Projected Mode



3 Can focus sound only at the place you want.3Ultrasonic emitter devices are thin and flat and do not

require a mounting cabinet.3 T he focused or directed sound travels much faster in a

straight line than conventional loudspeakers.3 Dispersion can be controlled - very narrow or wider to

cover more listening area.3 Can reduce or eliminate the feedback from microphones.3 Highly cost effective as the maintenance required is less

as compared to conventional loud speakers and have longer

life span.3 Requires only same power as required for regular

speakers.3 T here is no lag in reproducing the sound.



y Automobiles: Beam alert signals can be directlypropagated from an announcement device in thedashboard to the driver. Presently Mercedes - Benzbuses are fitted with audio spotlighting speakers so that

individual travelers can enjoy the music of there oninterest.



y Retail sales: Provide targeted advertising directly atthe point of purchase.

y Public announcement: Highly focused announcement innoisy environments such as subways, airports, amusementparks, traffic intersections etc.



y Entertainment system: In home theatre system rearspeakers can be eliminated by the implementation of audiospotlighting and the properties of sound can be improved.

y Museums: In museums audio spotlight can be used to

describe about a particular object to a person standing infront it, so that the other person standing in front ofanother object will not be able to hear the description.



y Safety officials: Portable audio spotlighting devicesfor communicating with a specific person in a crowd ofpeople.

y Emergency rescue: Rescuers can communicate with

endangered people far from reach.y Military applications: Ship - to ² ship communications and

shipboard announcements.

y Audio/Video conferencing: Project the audio from aconference in four different languages, forma single

central device without the need for headphones.y Sound bullets: Jack the sound level 50 times the human

threshold of pain, and an offshoot of audio spotlightingsound technology becomes a non-lethal weapon



y Even the best loudspeakers are subject to distortion andtheir Omni directional sound is annoying to the people inthe vicinity who do no wish to listen. Audio spotlightingsystem holds the promise of replacing conventional

speakers. It allows the user to control the direction ofpropagation of sound. T he audio spotlight will force peopleto rethink their relationship with sound. Audiospotlighting really "put sound where you want it".



y Audio spotlighting is really going to make a revolution insound transmission and the user can decide the path inwhich audio signal should propagate. Due to theunidirectional propagation it finds application in large

number of fields. Audio spotlighting system is going toshape the future of sound and will serve our ears withmagical experience.



y www.thinkdigit.com

y www.holosonics.com

y www.spie.org

y www.

how

stuffw

orks.

comy www.abcNEWS.com

y www.silentsound.co.za

y www.wikipedia.org

y www.techalone.com

audio spotlighting by bharadwaj

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