UPDATE: An earlier version of this blog incorrectly described the technology used in an advertisement for the A&E's TV show Paranormal State. The technology, developed by the Holosonic Research Lab, uses a beam of ultrasound as a "virtual source", which changes into audible sound as it travels through the air. Please read the technology's inventor, F_J_Pompei's comment or visit the Holosonic Research Labs site to learn more.
The folks who heard the ad for A&E's TV show Paranormal State emitted from a billboard in New York City's Greenwich Village must have thought it was pretty weird. As they walked into the targeted area they were exposed to highly focused sound. One big advantage of the technology is that it doesn't contribute to ambient-noise pollution. I went to the Village a few days ago to check out the technology, but A&E had already pulled the plug. A&E's PR agency told me the speakers were only active during the first week of the campaign, so you gotta wonder, if it was such a great idea, why turn it off? The billboard is still there.
The phenomenon was covered in a terrific segment on the December 14 On the Media radio program on my local NPR station, WNYC.
The "Audio Spotlight" technology used in the billboard was developed by Holosonic Research Lab. Their Web site claims that "through a combination of careful mathematical analysis and engineering insight, the Audio Spotlight sound system has become the very first, and still the only, sound beam system which generates low-distortion, high-quality sound in a reliable, professional package." Well, I'm not so sure about that.
American Technology Corporation's HyperSonic technology also focuses sound into small beams. The Brooklyn Historical Society is currently using Hypersonic speakers in an exhibit, "In Our Own Words: Portraits of Brooklyn's Vietnam Veterans." The show features life-size photographs of the veterans, and when you stand in front of the portrait, the sound system automatically turns on and you hear the soldiers' pre-recorded stories. Many visitors can simultaneously experience the exhibit without hearing other sounds (because the sound is so tightly localized each patron hears only the intended sound).
I found the Hypersonic system worked quite well, but its fidelity was rather limited (it sounded like a small table radio). The oral histories are really interesting, and the Brooklyn Historical Society has a number of exhibitions on view. Check it out.