audio spotlighting new

7/29/2019 Audio Spotlighting New

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Dept. of E&C 1 BIT, MANGALORE

1.INTRODUCTIONHi-fi speakers range from piezoelectric tweeters to various kinds of mid-range speakers

and woofers which generally rely on circuits and large enclosures to produce quality

sound, whether it dynamic, electrostatic or some other transducer based design. Engineers

have struggled for nearly a century to produce a speaker design with the ideal 20Hz to

20,000Hz capability of human hearing. When you listen to sound over loudspeakers, you

dont have any control over where the sound goes. Sometimes you don't want it to go

everywhere. Scientists have devised a way to solve that problem. They have figured outhow to steer sounds by aiming them only where he wants them to go with a device they

call Audio Spotlight.

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

light beams coming out of a flash light. By shining sound to one location, Specific

Listeners can be targeted with sound without others nearby hearing it, i.e. to focus the

sound into a coherent and highly directional beam. It makes use of non-linearity property

of air.

Imagine projecting sound in a narrow beam, much like the light from a spotlight!

In the past we were limited by sound invading all of the space surrounding the

loudspeaker or sound source. Not anymore! With the Audio spotlighting Sound systems,

you can put sound wherever you want. With a spotlight, when you step into the beam of

light, you are clearly illuminated by the light. When you step out of the beam, you are lit

only by the background light. Similarly you can't see the beam of sound, but when you

step into it, you can hear the sound or narration inside! Step back out of the beam and the

sound is gone! Stepping into the directional sound beam is like putting on a set of virtual

headphones. You can now have several different soundtracks or musical styles co-exist in

one small space, heard only by those who should.

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. When in audible


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ultrasonic pulses are fired into the air, it spontaneously converts the inaudible ultrasound

into an audible sound. A device known as parametric array employs the non-linearity of

the air to create audible by products from inaudible ultrasound, resulting in extremely

directive and beam like sound. This source can projected about an area much like a

spotlight and creates an actual specialized sound distant from a transducer. The

ultrasound column acts as a airborne speaker, and as the beam moves through the air

gradual distortion takes place in a predictable way. This gives rise to audible components

that can be accurately predicted and precisely controlled.

Sound from ultrasound is the name given here to situations when modulated

ultrasound can make its carried signal audible, without needing a receiver set. This

happens when the modulated ultrasound passes through anything which behavesnonlinearly and thus acts intentionally or unintentionally as a demodulator.

Also, problems with creating low bass tones will keep Audio spotlighting systems

out of Audio philes for the present. On the other hand, this is not preventing Sony from

incorporating the technology in plasma screens for specialty applications. Widespread

application of Audio spotlighting could still be years away, but with companies like Sony

interested, it can only speed mainstream adoption of the technology.


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2.HISTORY

History is replete with rival inventors battling one another to bring breakthrough creations

to market. Howe and Singer over the sewing machine, Bell and Gray over the telephone,

Edison and Swan over the light bulb.

Now, in that same tradition, two inventors Elwood Woody Norris of Poway, CA

based American Technology Corporation (ATC), and F. Joseph Pompei, of Watertown,

MAs Holosonic Research Labs, have harnessed the same scientific principle to create

competing directional-sound systems.

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 dating back to the 1960s. They called this device a

parametric array. In 1975, an article cited the nonlinear effects occurring in air.

Over the next two decades, several large companies, including Matsushita, NC

Denon, and Ricoh attempted to develop a loudspeaker based on this principle. They were

successful in producing some sort of sound, with extremely high levels of distortion

(>50).

Later during the spring of 1996, Elwood Woody Norris one of the founders of

American Technology Corporation was working blind to his competitor in the East within

his garage in Poway CA. He felt that ultrasound could be used to create a sound beam. In

July the same year, he felt that he had a breakthrough and he rushed off to the patent

office, and patented the same.

In 1998, Joseph Pompei presented the paper The Use of Airborne Ultrasonic for

generating Audible Sound Beams to the Audio Engineering Society, at their 105th

Convention in san Francisco CA. In 1999 he founded holosonic Research Labs or

Holosonics to commercialize this technology. He named it Audio spotlighting.


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Figure 2.1: FJOSEPH POMPEI at the MIT lab .propagation of sound from audio

spotlighting device.


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3. TECHNOLOGY OVERVIEW

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 1960s. 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 percent). In 1990s, Woody Norrisa

Radar Technician solved the parametric problems of this technology.

Audio spotlighting is a paradigm shift in sound production based on solid

principles of physics. Audio spotlighting technology projects a column of modulated

ultrasonic frequencies in to the air. These ultrasonic frequencies are inaudible by

themselves. However ,the interaction of the air and modulated ultrasonic frequencies

creates audible sounds that can be heard along a column. This audible acoustical sound

wave is caused when the air down-converts the ultrasonic frequencies to the lower

frequency spectrum that humans can hear.

Audio spotlighting technology works by emitting harmless high frequency

ultrasonic tones that we cannot here. These tones use the non-linearity (fig 3.1) property

of air to create new tones that are within the range of human hearing. The result is an

audible sound. The acoustical sound wave is created directly in the air.

In an Audio spotlighting system, there are no voice coils, cones, crossover

networks or enclosures. The result is sound with a potential purity and fidelity which we

attained never before. Sound quality is no longer tied to speaker size. The Audiospotlighting system holds the promise of replacing conventional speakers in homes,

movie theatres, and automobiles everywhere.


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Figure 3.1: Non linear medium

Figure 3.2: Pressure v/s distance curve

At normal atmospheric pressure and a temperature of 20rC, a small audio signal

travels through air at approximately 300m/sec. As the amplitude of the sound signal

increases to more than approximately 100 dB, the speed of sound changes over the course

of a single cycle. The upper part of the waveform sufficiently compresses air molecules to

increase the local temperature and pressure and, therefore, slightly boost the speed of

sound. Likewise, the negative portion of the waveform slows sound propagation. These

speed variations result in a distorted waveform that resembles a triangular wave

(fig3.2).Because triangular waves are rich in harmonics, the speed variations demodulate

the ultrasound signal. The blue line in fig-3.2 is a pure sine wave, and the red represents

the same form after it has propagated through the nonlinear air for a time.


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3.1 Conventional sound:

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. Conventional 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 nature, sound travels in waves spreading in every direction, bouncing of some

surfaces and being absorbed by others. It is certainly not linear. It helps to visualize the

traditional loudspeaker as a light bulb. As with the light bulb, a traditional loudspeaker

radiates sound fairly uniformly in all directions. A listener can stand anywhere in an

acoustical environment and point to the speaker as the source of the sound. Audio

spotlighting technology is much more analogous to the beam of light from a flashlight

.Figures 3.3 shows the conventional speakers distribution of sound and figure 3.4 shows

the beam of sound targeted to particular place. If you stand to the side or behind the light,

you can only "see" the light when it strikes a surface. Audio spotlighting technology issimilar in that you can direct the ultrasonic emitter toward 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 from the reflection of the wall. Every form of distortion contributed

by a conventional loudspeaker is traceable to some aspect of its mechanical nature, mass,

magnetic structure, enclosure design, cone construction, etc. All form an important part ofthe final product's capability to perform its function in as perfect a manner as possible.


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Figure 3.3: conventional speakers.

Speaker cone motion is subject to the laws of physics. This all-important element

,more than any other in a speaker system, affects the overall purity of sound and can be a

source of various forms of distortion. Ideally, when reproducing sound, the speaker cone

should follow precisely the delicate nuances of any electrical waveform presented to it.

The cone or radiating surface of a perfect loudspeaker would have virtually no mass or

resonances over the entire range of hearing, and would offer perfect linearity while at the

same time being able to couple enough energy into the air to produce any sound level

desired.

Audio spotlighting technology does precisely that. It provides linear frequency

response with virtually none of the forms of distortion associated with conventional

speakers. Physical size no longer defines fidelity. The faithful reproduction of sound is

freed from bulky enclosures. There are no woofers, tweeters, crossovers, or bulky

enclosures .Also, it is now possible to dramatically minimize room effects in a listening

environment.


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Figure 3.4: audio spotlighting.

3.2 Range of human hearing:

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

the human hearing is expressed as a percentage 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 of frequencies. In order to deal with this,

speaker manufacturers carve the audio spectrum into smaller sections (fig3.5), and make

use of multiple transducers and crossovers as necessary. They range from piezoelectric

tweeters that recreate the high end of the audio spectrum, to various kinds of midrange

speakers and woofers that produce the lower frequencies. Using a technique of

multiplying audible frequencies upwards and superimposing them on a "carrier" of

say,200,000 cycles the required frequency shift for a transducer would be only 10.

Whether they are dynamic, electrostatic, or some other transducer-based design,

all loudspeakers today have one thing in common: they are direct radiating i.e., they are

fundamentally a piston-like device designed to directly pump air molecules into motion to

Create the audible sound waves we hear. Audio spotlighting technology produces sound

in the air indirectly as a by-product of some other process. Using Audio spotlighting

technology, it is possible to design nearly a perfect transducer.


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Depending on the user requirements the bandwidth of Audio spotlighting unit can

be adjusted. The red plot shows the normal usage. The blue plot is the Bass cut plot,

where the lower frequencies are cut. This is very useful for speeches. The black plot is the

Bass boost plot, where the lower frequencies are given importance. This is very useful for

musical concerts.

Figure 3.5: audio spectrum.

3.3 Working of Audio spotlighting system:

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

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

ultrasonic frequencies range. 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. The model of spotlighting emitter is shown in figure3.7.


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Figure 3.6: Plot of bass cut, bass boost and normal sound.

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

property of air comes into action. A normal sound wave is a small pressure wave that

travels through the air. As the pressure goes up and down, the nonlinear nature of the air

itself lightly changes the sound wave. If there is 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. If the audio spectrum could be superimposed on this high frequency carrier,and emitted into the air as an ultrasonic acoustical wave front, the only thing remaining

would be to down convert the ultrasonic energy to sonic energy we could hear. This

ultrasonic sound wave (beyond the range of human hearing) can be sent in to the air with

sufficient volume to cause the air to create the required new frequencies. Sincewe cannot

here the ultrasonic sound, we only hear the new sounds that are formed by the non linear

action of the air.


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Figure 3.7: audio spotlight emitter.

Example:

In order to generate a frequency (sound) of 1000Hz, we use ultrasonic waves of50,000Hzand 51,000Hz frequency. These frequencies, due to nonlinearity and also distortion

produce 101,000Hz (inaudible) and 1000Hz (audible) which is the required

frequency.51,000+50,000=101,000Hz

51,000-50,000=1000Hz

Thus in an audio spotlighting there are no actual speakers that produces the sound

but the ultrasonic envelope acts as the airborne speaker. The directivity of the beam i.e,output of the system is shown in the figure-3.8.


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Figure 3.8: Beam Directivity

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

reproduction of sound is feed 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 from the reflection of the wall. For the maximum volume (sound

level) that trade show use demands, it is recommended that the audio spotlight speakers,

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.

Figure 3.9: computer simulation of sound beam.


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By creating a complex ultrasound waveform(using a parametric array of

ultrasound sources)figure-3.9 shows computer simulation of sound propagation with

complex sets, many different sources of sound can be created. If their phases are carefully

controlled, then these interfere destructively laterally and constructively in the forward

direction, resulting in a collimated sound beam or audio beam or audio spotlight. Today,

the transducers required to produce these beams are just half an inch thick and

lightweight, and the system required to drive it has similar power requirements to

conventional amplifiers technology.

3.4 Beam Dispersion

Figure 3.10: Dispersion of sound beam

In general, the dispersion is less than 3 in either direction or a total of 6 overall(fig3.10). Dispersion of the audio wave front can be tightly controlled by contouring the face

of the audio spotlighting ultrasonic emitter. For example, a very narrow wave front might

be developed for use on the two sides of a computer screen while a home theater system

might require a broader wave front to envelop multiple listeners.

In addition, audio spotlight does not follow the traditional loudspeaker inverse-

square law, which dictates that you have a 6dB decrease in level for every doubling of the


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distance from the source. This fact means that Audio spotlight can travel much greater

distances while maintaining intelligibility than the sound from conventional speakers.

3.5 Why Ultrasonic?

Directivity of the wave depends on its wavelength compared to the transmitting surface.

The larger the source is compared to the wavelength of the sound waves, the more

directional beam results. Assuming that HSS uses 48 kHz, following calculations couldbe

made. The speed of sound is about 300 m/sec, or 30,000 cm/sec.

Speed = (wavelength)*(frequency)

=> Wavelength=speed/frequency

i.e., 30,000/48,000 = 0.63 cm.

Normally, the emitter's frontal area is 28 cm x 28 cm, or approx 44 wavelengths

square. This fact is the basic source of the device's tight directionality. When an emitter's

size approximates the wavelength of the emitted signal, a spherical wave front is

produced (fig 3.12a), which expands with a surface area proportional to the square of the

distance from the emitter; thus producing inverse-square dispersal of energy across the

expanding surface.

Figure 3.11: Types of ultrasonic emitters


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A frequency of 1000Hz, for instance, yields a wavelength of 30 cm or about one

foot. Thus a signal in this frequency range, produced by a normal speaker whose diameter

might be approximately one foot, will produce a spherical wave front. However when the

wavelength is a small fraction of the size of the emitter, an essentially flat wave front is

produced (fig 3.11b). If it were truly flat and constrained to a channel, such a signal

would lose strength only due to interactions with the channel, and could travel very long

distances. Since our Audio spotlight beam is not in a channel, it will lose some energy to

adjacent air. The ultrasound, whose wavelengths are only a few millimeters long, are

much smaller than the source, and consequently tend to travel in a straight line. Of course,

this ultrasound, which contains frequencies far outside our range of hearing, is completely

inaudible. But as the ultrasonic beam travels through the air, the inherent properties of the

air cause the ultrasound to distort (change shape) in a predictable way. This distortiongives rise to frequency components in the audible bandwidth. By generating the correct

ultrasonic signal, we can create, within the air itself, essentially any sound desired.

Both audible sound waves from traditional speakers and ultrasound waves from a

directional-sound system distort when they travel through the air. But, in a traditional

sound system, the distortion slightly degrades the sound a listener ultimately hears. But in

a directional-sound system, the distortion is actually the mechanism that generates theaudible sound, breaking the ultrasound waves into lower-frequency, audible sound waves

along a straight, narrow path. When the waves encounter a solid object or person ,they

slow, distort and crash together. The result is the ultrasonic waves re-create the original

sound in the air around the object, so humans can hear it. Variations in the speed of sound

cause this phenomenon. Thus, sound from a distant Audio spotlight speaker seems like its

right at your ears because it is actually being created right at your ears. If you step out of

the beam, the waves have nothing to distort and mix them, so the inaudible ultrasonic

waves slide silently past.

Where,

p2(x,t)=Audible secondary pressure wave

Figure 3.12: Equation


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K = physical parameter

Pc=Pressure of ultrasonic carrier.

E(x,t)=Envelope function (DSB)

Previous equation says that the audible demodulated ultrasonic pressure wave (output

signal) is proportional to the twice differentiated, squared version of the envelope

function (input signal).

3.6 COMPONENTS OF AUDIO SPOTLIGHTING SYSTEM:

1. Power Supply.

2. Frequency oscillator.

3. Modulator.

4. Audio signal processor.

5. Microcontroller.

6. Ultrasonic amplifier.

7. Transducer.

3.6.1 Power Supply:

Like all electronic systems, the audio spotlighting system works on DC Voltage,

ultrasonic amplifier requires 48v for its working and low voltage. For microcontroller and

other processing unit management.

3.6.2 Frequency oscillator:

The frequency oscillator generates ultrasonic frequency signals in the range of (21,000Hz

to 28,000 Hz) which is required for the modulation of information signals.


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Figure 3.13: Block Diagram of An Audio Spotlighting System.

3.6.3 Modulator:

In order to convert the source program material into ultrasonic signals, a modulation

scheme is required. In addition, error correction is needed to reduce distortion withoutloss of efficiency. The goal, of course, is to produce audio in the most efficient manner

while maintaining acceptably low distortion levels.

A DSB scheme is straightforward way to generate the required ultrasonic

frequencies for a given base band signal. From the basic principles of the Fourier

analysis, multiplication in the time domain is analogous to convolution in the frequency

domain. Convolution between a baseband signal and a carrier frequency effectively

images the base band signal around both sides of the carrier frequency spectral


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component, as shown in Fig3.8. We know that for a DSB system, the modulation index

can be reduced to decrease distortion, because total harmonic distortion increases

proportionally with the square of m. This is because as the side bands gain more power,

there is more cross interference between the side bands rather than between the side bands

and the carrier frequency component.

3.6.4 Microcontroller:

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 modulation and even switch mode

power supply would be effectively taken care of by a single embedded IC.

Figure 3.14: DSB Signal Representation

3.6.5 Audio signal processor:The audio signal is sent to an electronic signal processor circuit where equalization,

dynamic range control, distortion control and precise modulation are performed to

produce a composite ultrasonic waveform. This amplified ultrasonic signal is sent to the

emitter, which produces a column of ultrasonic sound that is subsequently converted into

highly directional audible sound within the air column.


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Since ultrasound is highly directional, the audio sound placement is precise. At the heart

of the system is a high precision oscillator in the ultrasonic region with a variable

frequency ranging from 40 to 50 kHz.

3.6.6 Ultrasonic Amplifier:

High efficiency ultrasonic power amplifiers amplify the management of the system. In the

future version, it is expected that the whole process like functional management, signal

processing, double side band modulation and even switch mode power supply would be

effectively taken care of by a single embedded IC.

3.6.7 Transducer:

The most active piezo film is polyvinalidene difluoride. This film is commonly used in

many industrial and chemical applications.

In order to be useful for ultrasonic transduction, the raw film must be polarized or

activated. This is done by one of the two methods. One method yields a uniaxial film that

changes length along one axis when an electric field is applied through it. The other

method yields a biaxial film that shrinks/expands along two axes. Finally, the film needs

to have a conductive electrode material applied to both sides in order to achieve a uniform

electric field through it.

Piezoelectric films operate as transducers through the expansion and contraction

of X and/or Y axes of the film surface. For use as a hypersonic sound emitter, the film is

to be curved or distended. The curving results in expansion and contraction in the Z axis,

generating acoustic output.

The music or voice from the audio source is converted into a highly complex

ultrasonic signal by the signal processor before being amplified and emitted into the air

by the transducer. Since the ultrasonic energy is highly directional, it forms a virtual

column of sound directly in front of the emitter, much like the light from a flash light.


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Figure 3.15: Piezo sound emitter

Fig 3.15 shows the structure of piezo sound emitter. When a voltage is applied

across the pins, the red element gets longer while the blue one shortens, causing a bend in

the piezo. When the polarity changes, the opposite bend occurs. The maximum

displacement change is in the center of the element where the cone is attached.

The latest ATC parametric sound generator is a monolithic, thin film structure thatmaintains coherent amplitude and phase across the entire device in a package measuring

less than a half-inch thick . Because the emitter is larger than the wavelength of the

frequencies involved, it emits the ultrasound wave as a pure plane wave with virtually no

expansion in the beam diameter with distance.

Figure 3.16: Parametric Loudspeaker, Amazing Audio Spotlight.


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It is 1.27 cm thick and 17 inch in diameter. It is capable of producing audibility up

to200 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 properly of air.


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4.MODES OF LISTENING

There are two modes of listening:

1. Direct Mode.

2. Projected Mode.

Figure 4.1: directed audio and projected audio

4.1 Direct Mode

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. This method is appropriate when we want to restrict the audio in a specific

area .Fig 4.1 shows the concept of direct mode.

4.2 Projected 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 is

present. This method is appropriate when we want to send the information to a large

number of people. Fig 4.1 shows the concept of virtual mode.


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5.ADVANTAGES AND DISADVANTAGES5.1 ADVANTAGES:

i. Small size:Audio spotlighting not only has the conventional speaker's crossover network and

enclosure been eliminated, but the ultra-small radiating ultrasonic emitter is so small and

light-weight that the inertial considerations ordinarily associated with traditional direct

radiation speakers are virtually non-existent. The voice coil and support structure

normally associated with the conventional speaker used to attach the moving cone in

place are eliminated.

ii. Single source:Audio spotlighting has the ability to produce nearly the entire audible spectrum of

frequencies from a single source. Hence the improvement in phase response, time

alignment, and frequency response becomes obvious.

iii. Ultimate control in audio placement/Highly directional:Audio spotlight can focus sound only at the place where we want it. This is achieved by

controlling the dispersion of the wave. These focused sound travels much farther in a

straight line than conventional counterpart.

iv. Minimizes noise pollution:Audio spotlight reduces the unnecessary noise from public functions or gatherings.

v. Ease of installation:Audio spotlight reduces the unnecessary noise from public functions or gatherings.

vi. 5.6 Lowest maintenance cost:Since Audio spotlight system has no mechanical, and very few electrical components, the

maintaining cost very less.


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vii. Reduced feedback:As Audio spotlight systems allow us to direct the produced audio away from any live

microphone, the tendency of feedback is significantly reduced.

viii. There is no need to worry about pets:Dogs and cats can hear sounds up to perhaps 40,000 Hz, and Audio spotlight system

operates well above this range.

5.2 DISADVANTAGES:

i. Lack of mass production i.e, each unit must be handmade.ii. The most common form of distortion is clipping. An LED on top of the Audio

spotlight system reports clipping, which is also perceptible to the listener as a kind

of a 'chirping' effect. If any signal produces distortion, the input level of the source

is reduced until perceptible distortion is eliminated.


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6. APPLICATIONS

6.1 Automobiles:

Beam alert signals can be directly propagated from an announcement device in the

dashboard to the driver. Presently Mercedes Benz buses are fitted with audio spotlighting

speakers so that individual travelers can enjoy the music of there on interest.

Figure 6.1: Benz car

6.2 Retail sales:

Provide targeted advertising directly at the point of purchase.

Figure 6.2: A retail shop

6.3 Safety Officials:

Portable audio spotlighting devices for communicating with a specific person in a crowd

of people.

6.4 Public Announcement:

Highly focused announcement in noisy environments such as subways, airports,

amusement parks, traffic intersections etc. By maintaining a beam of sound, across the

traffic, traffic police can use audio spotlighting to help the blind people cross the road at

the signals.


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Figure 6.3: Public announcement

6.5 Entertainment Systems:

In home theatre system rear speakers can be eliminated by the implementation of audio

spotlighting and the properties of sound can be improved.

Figure 6.4: Home theatre system

6.6 Museums:

In museums audio spotlight can be used to describe about a particular object to a personstanding in front it, so that the other person standing in front of another object will not be

able to hear the description.

Figure 6.5: Museum

6.7 Military Applications:

Ship to ship communications and shipboard announcements. And also it is used to

misguide the enemy by creating the false shouting area away from the military camps.


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6.8 Political:

With the help of HSS international gatherings, such as the United Nations, SAARC

summit could have translated speech beamed directly to individuals: Spanish at one seat,

Hindi at the other and Arabic at the next. All this without interference or individual

earphones.


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7.CONCLUSION AND ENHANCEMENTS

Being the most radical technological development in acoustics since the coil loudspeaker

was invented in 1925... The audio spotlight will force people to rethink their relationshipwith sound. Audio spotlighting is going 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 its finds applications in large number of fields. The main

intention of Audio spotlighting system is to reduce the unnecessary sound and to promote

peace and quiet environment. With the companies like Sony and Bose interested, it is

going to shape the future of sound and will serve our ears with magical experience.

The audio spotlighting holds the promise of replacing conventional speakers.

Ultrasonic emitters have super high impedance, which allows low current in power

amplifiers making them lighter. The future developments of this technology include a full

functioning embedded system, including modulation, audio processing and distortion

control.


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