Conferencing without echo cancellation

The future of large board room conferencing system may not involve echo cancellation. There is a company in the Boston area that makes directional audio tiles that can be installed in the ceiling above conference room seats. The tiles are manufactured by

Holosonic and the product is called Audio Spotlight. The devices come in a 16″ and 24″ format and can replace a standard ceiling tile. The technology is described on the Holosonic web page, but here is a brief extraction.

“The ultrasound has wavelengths only a few millimeters long, which are much smaller than the source, and therefore naturally travel in an extremely narrow beam.

Of course, the 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 change shape in a predictable way. This gives rise to frequency components in the audible band, 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 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.

Often incorrectly attributed to so-called “Tartini tones”, the technique of using high-frequency waves to generate low-frequency signals was pioneered over forty years ago. Over the past two decades, many others have attempted – and failed – to use this technique to make a practical audio source.

Through a combination of careful mathematical analysis and engineering insight, the patented Audio Spotlight sound system has become the very first, and still the only, truly directional audio system which generates high quality sound in a reliable, professional package.”

This technology is interesting because:

  •  the beam is very tight and can be directed away from the conference microphone array.
  • The fact that the carrier is ultra-sonic means that it could be filtered by the microphone array.
  • Each audio source could be a different language so that everyone around the table could understand a multi-language conference.

Echo cancellation is complicated and the difficulty increases with more sources and objects that effect the echo path. By controlling what audio reaches the microphone array we can greatly simplify the process. This effects both complexity and cost.


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