AUDIO SPOTLIGHTING.doc (Size: 892 KB / Downloads: 1104)
Audio spot lighting is a very recent technology that creates focused beams of sound similar to light beams coming out of a flashlight. By Ëœshiningâ„¢ sound to one location, specific listeners can be targeted with sound without others nearby hearing it. It uses a combination of non-linear acoustics and some fancy mathematics. But it is real and is fine to knock the socks of 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 and as the beam moves through the air gradual distortion takes place in a predictable way due to the property of non-linearity of air. This gives rise to audible components that can be accurately predicted and precisely controlled. Joseph Pompeiâ„¢s Holosonic Research Labs invented the Audio Spotlight that is made of a sound processor, an amplifier and the transducer. The American Technology Corporation developed the HyperSonic Sound-based Directed Audio Sound
System. Both 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 huge commercial market in entertainment and consumer electronics and technology developers are scrambling to tap in to the market. Being the most recent and dramatic change in the way we perceive sound since the invention of coil loud speaker, audio spot light technology can do many miracles in various fields like Private messaging system, Home theatre audio system, Navy and military applications, museum displays, ventriloquist systems etc.
Thus audio spotlighting helps us to control where sound comes from and where it goes!
1.0 INTRODUCTION 3
2.0 THEORY 6
2.1 TECHNOLOGY OVERVIEW 10
2.2 COMPONENTS AND SPECIFICATIONS 11
2.2.1 SOUND BEAM PROCESSOR/AMPLIFIER 11
2.2.2 AUDIO SPOTLIGHT TRANSDUCER 12
2.3 NON-LINEARITY OF AIR 13
2.4 DIRECT AUDIO AND PROJECTED AUDIO 20
3.0 SPECIAL FEATURES 24
4.0 APPLICATIONS/ FUTURE EXPANSIONS 25
5.0 CONCLUSION 28
JUST WHAT IS AUDIO SPOTLIGHTING
Audio spot lighting is a very recent technology that creates focused beams of sound similar to light beams coming out of a flashlight. By Ëœshiningâ„¢ sound to one location, specific listeners can be targeted with sound without others nearby hearing it,ie to focus sound into a coherent and highly directional beam . It uses a combination of non-linear acoustics and some fancy mathematics. But it is real and is fine to knock the socks of any conventional loud speaker.
The Audio Spotlight & Hyper Sonic Sound Technology (developed by American Technology Corporation), uses ultrasonic energy to create extremely narrow beams of sound that behave like beams of light. Audio spotlighting exploits the property of non-linearity of air. When inaudible ultrasound pulses are fired into the air, it spontaneously converts the inaudible ultrasound into audible sound tones, hence proved that as with water, sound propagation in air is just as non-linear, and can be calculated mathematically. A device known as a parametric array employs the non-linearity of the air to create audible by-products from inaudible ultrasound, resulting in an extremely directive, beamlike wide-band acoustical source. This source can be projected about an area much like a spotlight, and creates an actual spatialized sound distant from the transducer. The ultrasound column acts as an 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.
IN TO THE DEPTHS OF AUDIO SPOTLIGHTING TECHNOLOGY
What ordinary audible sound & Conventional Loud Speakers lack
What we need
About a half-dozen commonly used speaker types are in general use today. They range from piezoelectric tweeters that recreate the high end of the audio spectrum, to various kinds of mid-range speakers and woofers that produce the lower frequencies. Even the most sophisticated hi-fi speakers have a difficult time in reproducing clean bass, and generally rely on a large woofer/enclosure combination to assist in the task. Whether they be dynamic, electrostatic, or some other transducer-based design, all loudspeakers today have one thing in common: they are direct radiating-- that is, they are fundamentally a piston-like device designed to directly pump air molecules into motion to create the audible sound waves we hear. The audible portions of sound tend to spread out in all directions from the point of origin. They do not travel as narrow beamsâ€which is why you donâ„¢t need to be right in front of a radio to hear music. In fact, the beam
angle of audible sound is very wide, just about 360 degrees. This effectively means the sound that you hear will be propagated through air equally in all directions.
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, the less the beam angle, and hence, the more focused the sound. Unfortunately, most of the human-audible sound is a mixture of signals with varying wavelengthsâ€between 2 cms to 17 metres (the human hearing ranges from a frequency of 20 Hz to 20,000 Hz). Hence, except for very low wavelengths, just about the entire audible spectrum tends to spread out at 360 degrees. To create a narrow sound beam, the aperture size of the source also mattersâ€a large loudspeaker will focus 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. To ensure that the shortest audible wavelengths are focused into a beam, a loudspeaker about 10 metres across is required, and to guarantee that all the audible wavelengths are focused, even bigger loudspeakers are needed.
Here comes the acoustical device AUDIO SPOTLIGHT invented by Holosonics Labs founder Dr. F. Joseph Pompei (while a graduate student at MIT), who is the master brain behind the development of this technology.
FIG.1:-AUDIO SPOTLIGHT CREATES FOCUSED BEAM OF SOUND UNLIKE CONVENTIONAL LOUD SPEAKERS
Audio spotlight looks like a disc-shaped loudspeaker, trailing a wire, with a small laser guide-beam mounted in the middle. When one points the flat side of the disc in your direction, you hear whatever sound he's chosen to play for you â€ perhaps jazz from a CD. But when he turns the disc away, the sound fades almost to nothing. It's markedly different from a conventional speaker, whose orientation makes much less difference.
Fig 2:- F.JOSEPH POMPIE AT THE MEDIA LAB OF THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY DEMONSTRATES HOW INVISIBLE ULTRASOUND WAVES, AS ILLUSTRATED HERE, COULD HELP STEER SOUND.
2.1 TECHNOLOGY OVERVIEW
The Audio Spotlight & Hyper Sonic Sound Technology (developed by American Technology Corporation), uses ultrasonic energy to create extremely narrow beams of sound that behave like beams of light. Ultrasonic sound is that sound that has very small wavelengthâ€in the millimeter range and you canâ„¢t hear ultrasound since it lies beyond the threshold of human
2.2 COMPONENTS AND SPECIFICATIONS
Audio Spotlight consists of three major components: a thin, circular transducer array, a signal processor and an amplifier. The lightweight, nonmagnetic transducer is about .5 inches (1.27 centimeters) thick, and it typically has an active area 1 foot (30.48 cm) in diameter. It can project a three-degree wide beam of sound that is audible even at distances over 100 meters (328 feet). The signal processor and amplifier are integrated into a system about the size of a traditional audio amplifier, and they use about the same amount of power.
2.2.1 SOUND BEAM PROCESSOR/AMPLIFIER
Â¢ Worldwide power input standard
Â¢ Standard chassis 6.76/171mm (w) x 2.26/57mm (h)x 11/280mm (d), optional rack mount kit
Â¢ Audio input: balanced XLR, 1/4 and RCA (with BTW adapter) Custom configurations available eg. Multichannel
2.2.2 AUDIO SPOTLIGHT TRANSDUCER
17.5/445mm diameter, 1/2/12.7mm thick, 4lbs/1.82kg
Wall, overhead or flush mounting
Black cloth cover standard, other colours available
Audio output: 100dB max
~1% THD typical @ 1kHz
Usable range: 20m
Audibility to 200m
Optional integrated laser aimer 13/ 330.2mm and 24/ 609.6mm diameter also available
Fully CE compliant
Fully realtime sound reproduction - no processing lag
Compatible with standard loudspeaker mounting accessories Due to continued development, specifications are subject to change.
2.3 NON-LINEARITY OF AIR
Audio spotlighting exploits the property of non-linearity of air. When inaudible ultrasound pulses are fired into the air, it spontaneously converts the inaudible ultrasound into audible sound tones, hence proved that as with water, sound propagation in air is just as non-linear, and can be calculated mathematically. A device known as a parametric array employs the non-linearity of the air to create audible by-products from inaudible ultrasound, resulting in an extremely directive, beamlike wide-band acoustical source. This source can be projected about an area much like a spotlight, and creates an actual spatialized sound distant from the transducer. The ultrasound column acts as an 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. However, the problem with firing off ultrasound pulses, and having them interfere to produce audible tones is that the audible components created are nowhere similar to the complex signals in speech and music. Human speech, as well as music, contains multiple varying frequency signals, which interfere to produce sound and distortion. To generate such sound out of pure ultrasound tones is not easy. This is when teams of researchers from Ricoh and other Japanese companies got together to come up with the idea of using pure ultrasound signals as a carrier wave, and superimposing audible speech and music signals on it to create a hybrid wave. 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%. No single loudspeaker element can operate efficiently or uniformly over this range of frequencies. In order to deal with this speaker manufacturers carve the audio spectrum into smaller sections. This requires multiple transducers and crossovers to create a 'higher fidelity' system with current technology.
FIG.3:-PARAMETRIC LOUDSPEAKER- AMAZING AUDIO SPOTLIGHT
(Airborne ultrasounds of 28kHz are envelope-modulated with audio signals. Inherent non-linearity of the air works as a de-modulator. Thus de-modulated sounds impinge on our eardrums. We can hear those sounds! )
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%. Building a transducer that only needs to produce waves uniformly over only a 10% frequency range.
FIG.4:-SHOWING THE DIFFERENCE IN MODULATING AUDIBLE
FREQUENCIES WITH ULTRASONIC CARRIER
This is similar to the idea of amplitude modulation (AM), a technique used to broadcast commercial radio stations signals over a wide area. The speech and music signals are mixed with the pure ultrasound carrier wave, and the resultant hybrid wave is then broadcast. As this wave moves through the air, it creates complex distortions that give rise to two new frequency sets, one slightly higher and one slightly lower than the hybrid wave. Berktayâ„¢s equation holds strong here, and these two sidebands interfere with the hybrid wave and produce two signal components, as the equation says. One is identical to the original sound
wave, and the other is a badly distorted component. This is where the problem liesâ€the volume of the original sound wave is proportional to that of the ultrasounds, while the volume of the signalâ„¢s distorted component is exponential. So, a slight increase in the volume drowns out the original sound wave as the distorted signal becomes predominant. It was at this point that all research on ultrasound as a carrier wave for an audio spotlight got bogged down in the 1980s.
Focusing on the signalâ„¢s distorted component, since the signal componentâ„¢s behavior is mathematically predictable, the technique to create the audio beam is simple; modulate the amplitude to get the hybrid wave, then calculate what the Becktayâ„¢s Equation does to this signal, and do the exact opposite. In other words, distort it, before Mother Nature does it.
Finally, pass this wave through air, and what you get is the original sound wave component whose volume, this time, is exponentially related to the volume of the ultrasound beam, and a distorted component, whose volume now varies directly as the ultrasound wave.
By creating a complex ultrasound waveform (using a parametric array of ultrasound sources), 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 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 amplifier technology.
FIG.5:-COMPUTER SIMULATION OF SOUND PROPAGATION: COMPLEX SET OF HIGH-INTENSITY ULTRASOUND SIGNAINTERMODULATEAIR. AMONG THE PRODUCTS IS A COLLIMATED AUDIO "SPOTLIGHT".
2.4 DIRECT AUDIO AND PROJECTED AUDIO
There are two ways to use Audio Spotlight. First, it can direct sound at a specific target, creating a contained area of listening space which is called Direct Audio. Second, it can bounce off of a second object, creating an audio image. This audio image gives the illusion of a loudspeaker, which the listener perceives as the source of sound, which is called projected Audio. This is similar to the way light bounces off of objects. In either case, the soundâ„¢s source is not the physical device you see, but the invisible ultrasound beam that generates it
FIG.6:- DIRECT AUDIO AND PROJECTED AUDIO
Hyper Sonic Sound technology 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. Thus it helps to visualize the traditional loudspeaker as a light bulb, and HSS technology as a spotlight, that is 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, only from the reflection off the wall.
Contouring the face of the HSS ultrasonic emitter can tightly control Dispersion of the audio wave front. 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.
FIG.7:-CONVENTIONAL LOUDSPEAKER & ULTRASONIC EMITTER
3.0 SPECIAL FEATURES OF AUDIO SPOTLIGHT
A COMPARISON WITH CONVENTIONAL LOUD SPEAKER:-
Creates highly FOCUSED BEAM of sound
Sharper directivity than conventional loud speakers using Self demodulation of finite amplitude ultrasound with very small wavelength as the carrier
Uses inherent non-linearity of air for demodulation
Components- A thin circular transducer array, a signal processor & an amplifier.
Two ways to use- Direct & projected audio
Wide range of applications
Highly cost effective
4.0 APPLICATIONS OF AUDIO SPOTLIGHTING -TOWARDS THE FUTURE
"So you can control where your sound comes from and where it goes," says Joe Pompei, the inventor of Audio Spotlight. , Pompei was awarded a Top Young Innovator award from Technology Review Magazine for his achievements.
The targeted or directed audio technology is going to tap a huge commercial market in entertainment and in consumer electronics, and the technology developers are scrambling to tap into that market. Analysts claim that this is possibly the most dramatic change in the way we perceive sound since the invention of the coil loudspeaker. The technology that the Holosonics Research Labs and the American Technology Corporation are lining up may seem to be a novelty of sorts, but a wide range of applications are being targeted at it.
Continuing to improve on the commercial success of the Audio Spotlight sound system, Holosonics has announced that its next-generation laser-like sound system, with improved performance and lower cost, is now actively in production. These new systems are being exhibited at the 2004 Consumer Electronics Show in Las Vegas alongside MIT Media Lab technology.
The performance and reliability of the Audio Spotlight have made it the choice of the Smithsonian Institution, Motorola, Kraft, and Cisco Systems etc.
Holosonics put in four individual Audio Spotlights into the Daimler Chrysler MAXXcab prototype truck to let all the passengers enjoy their own choice of music. Boston Museum of Science - as well as the United States military.There is an even bigger market for personalized sound systems in entertainment and consumer electronics.
Holosonic Labs is working on another interesting application at the Boston Museum of Science that allows the intended listeners to understand and hear explanations, without raising the ambient sound levels. The idea is that museum exhibits can be discretely wired up with tiny speaker domes that can unobtrusively, provide explanations
. There are also other interesting applications that they are looking at, such as private messaging using this system without headphones special effects at presentations as well as special sound theme parks that could put up animated sound displays similar to todayâ„¢s light shows. Holosonic has installed their Audio Spotlight system at Tokyoâ„¢s Sega Joyopolis theme park.
The US Navy has installed sound beaming technology on the deck of an Aegis-class Navy destroyer, and is looking at this as a substitute to the radio operatorâ„¢s headphones.
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 relationship with soundÂ¦
So we can conclude- Audio Spotlighting really put sound where you want it and will be A REAL BOON TO THE FUTURE.
ENGINEERING PHYSICS By B.PREMLET