03-01-2011, 05:22 PM
[attachment=7924]
Submitted by
VEERENDRA SHETTY T P
INTRODUCTION
Hi-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 – 20,000Hz capability of human hearing. When you listen to sound over loudspeakers, you don't 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 out how 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.Audiospotlight exploits the property of non-linearity of air. When in audible 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 behaves nonlinearly
and thus acts intentionally or unintentionally as a demodulator.
For now, customers are testing out the technology for a variety of uses. But adoption
may be slow due to the cost of the system and the fact that each unit needs to be handmade.
Also, problems with creating low bass tones will keep Audio spotlighting systems out of
audiophiles 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.
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, MA’s 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%). This drawback caused the total abandonment of the technology by the end of the 1980's.
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”.
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 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 is a paradigm shift in sound production based on solid principles of physics. Audio spotlighting technology projects a column of modulated ultrasonic frequencies into 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 a 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 Audio spotlighting system holds the promise of replacing conventional speakers in homes, movie theatres, and automobiles everywhere.
