Technology

A new technology has been developed that can project a beam of sound so narrow that only one person can hear it. "Directed" audio sounds like it's coming from right in front of you even when transmitted from up to 200 meters away.

Joseph Pompei, a PhD student at the MIT Media Lab, decided to develop it while working at audio company Bose, which he joined at 16 as its youngest-ever engineer.

The Audio Spotlight transmitters generate a column of sound between three and five degrees wider than the transmitter. It converts ordinary audio into high-frequency ultrasonic signals that are outside the range of normal hearing. As these sound waves push out from the source, they interact with air pressure to create audible sounds.

High-frequency signals are easier to focus, and control like a flashlight, than sounds that are within the human range of hearing, which disperse in all directions. Ultrasonic signals decay more slowly than lower-frequency waves so they are easier to send farther.

The Audio Spotlight emits sounds in the 60-kilohertz range, which is well above the 20-KHz limit of human hearing.

The first experiments to use ultrasonic sounds were conducted underwater in the 1960s, and Japanese researchers made advances in the 1980s but were unable to create a commercial application for the technology.

Technical advice and consulting for Audio Spotlight!

Audio Spotlight - The Solution to one of life's many challenges
Did you ever need to put sound into just one small area of an exhibit or display? Ever struggle to make an environment more effective, engaging and quieter by eliminating overlapping sounds? Enter the Audio Spotlight!

Current / Previous Solutions
The Audio Spotlight is a relatively new product developed at MIT that allows the user to beam sound into very small area of an exhibit or display. The beam from an Audio Spotlight is just 18” to 24” across and can be projected up to 200 meters. Until approximately 5 years ago, directional speakers such as sound dome products and steered arrays had been used to create zones of sound. However, the sound projected from a sound dome or array is regular sound, shaped to remain in a smaller area. Once this standard sound leaves the confines of the dome, it immediately wants to spread out to fill up all of the space surrounding the dome. The sound from these more widely known products is about 60% directional at most.

The ultra sound beam from an Audio Spotlight, instead wants to remain in a narrow beam, more like the beam of light from a spotlight. As a result, the Audio Spotlight enables the exhibit designer and builder the ability to add sounds into very small spaces and create narration or musical environments where previously this had not been practical. This beam of sound is somewhere between 90-95% directional.

Advantages of the Audio Spotlight
The purpose of using the Audio Spotlight is to create atmospheres of sound within an exhibit without the use of sound partitioning. The Audio Spotlight keeps an exhibit space quieter by eliminating overlapping areas of sound that make an exhibit louder, annoying and confusing.

Normally sounds add up within a space increasing the ambient noise level within that space. If an exhibit has 20 people talking loudly, the exhibit gets louder. Every sound within the exhibit spreads out to fill that and the surrounding space. Thus, in an area like a trade show, where there are many people interacting, live presentations, and music playing in the background, the environment gets loud and even annoying very quickly. All of the sounds add up to create a louder environment or higher sound level. Since the sounds created by the Audio Spoltight are not heard outside the beam, many Audio Spotlights can be used in the same exhibit space without making that exhibit space any louder.

System Components
The Audio Spotlight equipment consists of a transducer (speaker), amplifier and coax cable connecting the two. Standard sound devices are used to create the source signal, such as DVD, CD or computers. The short wavelengths contained in the ultrasound beams, make the beam perform more like one of light than sound, so the sound projects straight from the transducer without spreading out to fill the room. The beam of sound is actually so focused that it will reflect off a hard surface, like a beam of light coming from a mirror.

History of Installations
The first Audio Spotlight was installed at Joypolis, Sega’s amusement park in Tokyo Japan more than five years ago. Audio Spotlights have been installed at the Bibliotheque Nationale de France (French National Library) and ACMI at Federation Square in Melbourne Australia for almost four years. In addition there are Audio Spotlights installed in several museums around the US, and even several retail stores. This technology is proven and really works!

Future Applications
Several of the automobile and electronics manufacturers around the world are currently experimenting with the Audio Spotlight. Imagine everyone being able to listen to a different radio station in each seat of the car during your next outing with the family or being able to watch TV late at night next to your spouse, without them hearing the audio part of the broadcast! Make no mistake, this is a world changing product, that is available now. The Audio Spotlight will help solve a problem that exhibit builders and designers have struggled with for a long time.

Transducer (Speaker) Positioning
For the maximum volume (sound level) that trade show use demands, it is recommended that the Audio Spotlight speaker, more accurately called a transducer, is mounted no more than 3 meters from the average listeners ears, or 5 meters in the air. The mounting hardware is constructed with a ball joint so that the Audio Spotlights are easily aimed wherever the sound is desired.

Transducer
The Audio Spotlight transducer is very discreet, at only 1.8cm thick. They come in two standard sizes 16" or 24”.

Amplifier
The transducers are driven by a small ultrasound amplifier 5cm W x 4.5cm H x 7cm L. The amplifier receives the input signal from a standard audio source such as a computer, CD player or DVD. The amplifier can currently push the sound signal through a cable 30 meters long without any in-line signal amplification. Developments are currently being tested which will extend that distance a great deal. The amplifier runs on a 24 DC Volt Laptop type power supply.

Sound Track Production / Product Audio Performance

The Audio Spotlight does not currently reproduce bass below 350 Hz well. As a result, the audio track is produced, equalized and mixed to eliminate unused tones. To create a more dynamic acoustic environment, the low tones can be added back into the space with a subwoofer. Of course the sounds from a subwoofer will not be directional, but luckily, bass heard by itself is very non-descript and thus, non-obtrusive. We have found that subwoofers are a non-distracting way to add the low tones back into the space without unnecessarily increasing the sound level or potential for audio related distraction.

Silent Sound can produce the soundtracks for the Audio Spotlight at reasonable rates or supply outboard equalizers and compressors depending on the program material or application.