Ultrasonic as a Sound Source

ULTRASONIC AS A SOUND SOURCE

  -Blog By Sufiyan A. Khan (Assistant Professor, ETC, ACET, Nagpur)

       Since the goal is a small loudspeaker but strong directivity, the only possible solution is to generate very small wavelengths - such as those of high-frequency ultrasound. The ultrasound used in Holosonic technology 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, 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 several 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 based on pioneering work at MIT in the early 2000's, 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.

  TECHNOLOGY

       The directivity (narrowness) of all wave producing sources depends on the size of the source compared to the wavelengths it generates. Because audible sound has wavelengths comparable to the size of most loudspeakers, sound generally propagates omni-directionally. Only by creating a sound source much larger than its wavelengths can a narrow beam be created. In the past, loudspeaker manufacturers have created large speaker panels or reflective domes to provide some directivity, but due to the sound's large wavelengths, the directivity of these devices is still extremely weak. To overcome these inherent limitations, we bend the laws of acoustics... and make a narrow beam of sound from only ultrasound. 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. Air converts this ultrasound sound into audible sound as it travels, making truly directional sound, literally out of thin air!

AUDIO SPOT LIGHT

     The Audio Spotlight is a revolutionary new audio technology that creates sound in a narrow beam, just like light. Aim the flat, thin speaker panel to your desired listening area, and provide...

       Since 2000, thousands of Audio Spotlight systems have been installed in a wide range of applications around the world. From museums, exhibits, kiosks, and digital signage to retail stores and special projects, hundreds of companies have chosen this unique, patented technology to provide high-quality, precisely controlled sound, while preserving the quiet. Based on research by MIT scientists, Audio Spotlight systems use entirely different physics to create sound in true, ultra-tight beams that are impossible with any other technology.

KEY FEATURES

• On-board playback via micro-SD Built-in amplifier/processor

• Visual display/interface

• IR remote control

• Proprietary Bass Enhancement

• Advanced audio processing algorithms

• Optimized preset modes

• VESA 100 mounting pattern

APPLICATION

      Audio Spotlight systems have been in use in thousands of installations all over the world since 2000. Customers include American Greetings, Best Buy, Boston Museum of Science, Cisco Systems, the Field Museum, the Guggenheim, Harvard Peabody Museum, Jack Morton Worldwide, Kaiser Permanente, Motorola, Science World BC, Tate Modern, Walt Disney, Western Union and the Yale Art Gallery.

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