Audio Spotlighting and Hypersonic Sound

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Audio Spotlight and Hypersonic Sound (HSS) Introduction

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 Spotlight or Hypersonic Sound systems, you can put sound wherever you want. Keep the analogy of a spotlight in mind. 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. Now imagine a beam of sound! You can’t see the beam, 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!
Imagine the ability to put sound wherever you want! We can now contain sound in a beam using an Audio Spotlight or Hypersonic Sound! Stepping into the directional sound beam is like putting on a set of virtual headphones. Imagine, you can now have several different soundtracks or musical styles co-exist in one small space, heard only by those who should.
We can deliver a specific message to a certain group or individual.
We can create a distinct musical atmosphere within a very small area.
This ability is possible using the Audio Spotlight or Hypersonic Sound directed audio sound systems.

How do these systems work?
The directivity (narrowness) of any wave producing source depends on the size of the source, compared to the wavelengths it generates. Audible sound has wavelengths ranging from a few inches to several feet, and because these wavelengths are comparable to the size of most loudspeakers, sound generally propagates omnidirectionally. Only by creating a sound source much larger than the wavelengths it's producing is it possible to create a narrow beam using a standard style loudspeaker and amplifier.
Clearly, having loudspeakers twenty meters wide is not very useful. So to make a narrow beam of sound from a small acoustic source, we instead generate only ultrasound.

The ultrasound, whose wavelengths are only a few millimetres long, are much smaller than the source, and consequently tend to travel in a straight line, much like the beam of light from a flashlight. 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 distortion gives rise to frequency components in the audible bandwidth, which can be accurately predicted, and therefore precisely controlled. By generating the correct ultrasonic signal, we can create, within the air itself, essentially any sound desired.

Note that the source of sound is not the transducer or physical device you see, but the invisible beam of ultrasound, which can be many meters long. This new sound source, while invisible, is very large compared to the audio wavelengths it's generating. So the resulting audio is now extremely directional, just like a beam of light.
For years scientists have used transducers for everything from medical ultrasound imaging to fishfinders (for other transducer applications click here), and now they have developed a practical way for us to use a directional "beam" of sound to communicate critical information to small groups or individuals within a crowd, using either the Audio Spotlight, or Hypersonic Sound system.
History of Directed Audio Sound System development also known as Audible Ultrasonic Speakers or 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 1960's. These early acoustics researchers successfully derived the formal mathematical basis for this effect, and developed innovative sonar systems with more directivity and bandwidth than would otherwise be available. They called this device a parametric array.

In 1975, the first publication appeared which demonstrated that these nonlinear effects indeed occur in air. While these researchers had not attempted to reproduce audio, they nonetheless proved that such a device may be possible. Over the next two decades, several large companies, including Matsushita (Panasonic), NC Denon, and Ricoh attempted to develop a loudspeaker based on this principle. While they were successful in producing some sort of sound, problems with cost, feasibility, and extremely high levels of distortion (>50% THD) caused the almost total abandonment of the technology by the end of the 1980's.

So WHO invented Hypersonic Sound?

Enter Dr. Joseph Pompei, Holosonics (Holosonic Research Lab) and the Audio Spotlight

While a graduate student developing '3D Audio' at Northwestern University in the late 1990's, Joseph Pompei had similar ideas of using ultrasound as a loudspeaker, largely to overcome deficiencies he saw with traditional methods of sound reproduction. After performing extensive research on the idea, he discovered a large body of knowledge in the field of nonlinear acoustics, and documentation of earlier attempts at using ultrasound as an audible source. Pompei was able to rectify many of the barriers which had plagued the earlier researchers. Through a combination of careful mathematical analysis and solid engineering, he was able to construct the very first, and one of the only, practical, high-performance audio beam systems.
Enter Elwood "Woody" Norris, American Technology Corporation (ATC) and Hypersonic Sound (HSS)

American Technology Corporation or ATC was founded in 1980, began trading publicly in 1982, and was recapitalized and redomiciled in 1992. Commencing in fiscal 1993, the Company obtained over $1.5 million from the sale of its patented EarPHONE™ technology which encompassed a miniature, in-ear speaker/microphone combination enabling hands-free communication for telephones, computers, and cellular phones. Elwood “Woody” Norris was one of the founders of American Technology Corporation.
During about the same time period, Spring of 1996, Elwood “Woody” Norris, was working blind to his competitor in the East within his garage in Poway CA. He also felt that hypersonic sound, or ultrasound could be used to create a sound beam. Woody had been a prolific career long inventor. In July of 1996, Woody felt that he had a breakthrough and he rushed off to the patent office, not realizing that other efforts had and continued to be made to perfect and patent the same directed audio speaker system technology. For additional insight into ATC's effort click here for an excerpt from USA Today

In 1998, Joseph Pompei presented the paper “The Use of Airborne Ultrasonics for Generating Audible Sound Beams” to the Audio Engineering Society, at their 105th Convention in San Francisco CA. At that time F. Joseph Pompei was working to complete his doctorate at the world renowned MIT Media Lab. Dr Pompei founded Holosonic Research Labs or Holosonics in 1999 in order to commercialize this technology.

Shortly thereafter in 1999, Holosonics made its first sale to Joypolis. Joypolis, Sega's Amusement park in Tokyo Japan purchased and installed the Audio Spotlight within one of its public entertainment areas. In 2001, the Bibliotheque Nationale de France (French National Library) purchased and installed several of these units. In 2002 the Audio Spotlight was used by the PGA of Europe to create zones of sound without making the golf course noisy or distracting for the players. At the Adelaide Festival 2002, in Australia, this technology was used to create zones of sound for personal entertainment within the crowd. F. Joseph Pompei, graduated Dr. Joseph Pompei from MIT during the summer of that same year.
Present

In 2003, Audio Spotlights were installed in Ingersoll Rand’s corporate showroom in South Carolina used at both the National Association of Broadcasters Show and American Society of Museums Show. In 2004 the Audio Spotlight was used at the National Home Builder’s Show and also installed at Disney’s Epcot Center and the Smithsonian Institute of Technology in Washington DC. Other prominent customers that installed Audio Spotlights in 2004 include the Boston Museum of Science and Tait Gallery in London, where the units are being used to narrate an exhibit of Picasso paintings.

World wide patents have been awarded for the technology used in the Audio Spotlight. American Technology Corporation has also been awarded application based patents for their technology.

Audio Spotlight vs Hypersonic Sound
At approximately the same time as the Audio Spotlight was being developed at MIT, Elwood "Woody" Norris was developing a product which creates a similar effect, namely, highly directional sound called Hypersonic Sound (HSS). Hypersonic Sound is manufactured at ATC - American Technology Corporation in San Diego, CA. The Audio Spotlight is manufactured by Holosonic Research Labs or Holosonics, in Watertown, MA. For more information click here for a link to Directional Sound History.
The Audio Spotlight separates the amplifier from the transducer. The transducer is thus, very thin at less than 1". Hypersonic Sound or HSS creates a sound beam using lower frequency ultrasound than the Audio Spotlight. HSS fits the whole product into a small metal box approximately 11" x 11" x 3.5". Like the Audio Spotlight, the beam of sound emitted by HSS is approximately the size of the transducer, so the 11" x 11" box emits a beam approximately 11" square. So how does one select which one to use - HSS vs. Audio Spotlight?
Hypersonic Sound vs. Audio Spotlight Comparison Chart

Feature or Benefit	Hypersonic Sound (HSS) by American Technology Corp	Audio Spotlight by Holosonics
Sound Quality - mid-range and highs	Compares well with performance of Audio Spotlight 18", but not nearly as good sounding as Audio Spotlight 24"	18" Very dynamic with little distortion 24" same as the 18" with the addition of one octave on the low frequencies
Sound Quality - lows (under 300 Hz)	virtually non-existent	virtually non-existent, has been successfully installed coupled with subwoofer to produce low frequency sounds
Product Durability / Longevity	HSS II is much more durable than the original versions. Still some question in our minds as to very long duration applications.	Proven - currently there are installations more than three years old. The Audio Spotlight by Holosonics is a fairly bullet-proof design, that holds up well in the field, even under continuous use.
Installations and Product history	currently no permanent real world installations	real world installations beginning in the year 2000 - continuously running Audio Spotlight installations since 2000
Ease of Installation / Hideability	equipment contained in box 11" x 11" x 3.5" thick - Sound source such as DVD or CD separate with direct input into Hypersonic Sound System	Audio Spotlight transducer (speaker) separate from amplifier. Transducer can be placed 100' from amplifier. Transducer is fully camaflougeable with the use of sublimation printable lycra speaker cover and blends in at only 1/2" thick. Sound source separate with direct input into amplifier
Rental Availability	no rentals currently available	rental fleet of 24 - 24" Audio Spotlights currently available for $325 / show day plus shipping from Muse Presentation Technologies
Purchase Pricing	lower than the Audio Spotlight but much more per square foot of coverage	18" - approximately 30% higher than HSS per unit, but 45% lower than HSS on a per square foot of sound zone coverage basis 24" - approximately 60% higher than HSS per unit, but 50-60% lower than HSS on a per square foot of sound zone coverage basis

We are the only distributor with experience selling and installing both Hypersonic Sound (HSS) by American Technology Corp and the Audio Spotlight by Holosonics. We will be happy to recommend the best product for your next project. Please Contact Us with any questions or for more information.