A high-powered Magnetic Audio Device that was designed as a non-lethal weapon might have music-related uses, after a demonstration revealed that the music of Queen and Frank Sinatra sounded decent at distances of up to one mile away.
Here’s the science. Light diffuses and grows weaker over distance because it’s not all of the same wavelength. Lasers, on the other hand, don’t diffuse, because their light has the same wavelength. Planar waves are the sonic equivalent of lasers: sound waves of identical frequency emanating from a flat panel.
Like lasers, planar waves don’t diffuse over distance. If you were to aim a magnetic audio device (MAD) directly at a crowd of people hundreds of meters away, they’d hear planar waves emanating from it as if they were standing right next to it, although the system can be affected by obstruction, wind gusts and bodies of water.
Because the frequency of the sound waves can change, so long as it changes identically across the board, such a system can play music or other forms of audio that include various frequencies.
Potential applications for MAD include the application of non-lethal force, according to the June 2 edition of the New Yorker. However, one can see Magnetic Audio Devices coming into play at outdoor music festivals too.
Here, non-lethal weapons expert Charles Heal describes the device’s sound quality to the New Yorker’s Alec Wilkinson:
“‘When he demonstrated the system, I went a hundred yards down the road, and he’s playing a Queen record,’ (Heal) said. ‘As the drummer is hitting his drum, I can feel it on my chest so tangibly that I look down to see if my shirt is moving.’ As I’m leaving, he says, ‘If you think that’s something, I can make the sound go a mile.’
“So we picked a date, and I brought a sixty-thousand-watt generator. We took a GPS and measured a mile, and I listened to a Frank Sinatra record and everything was there — the lyrics, the orchestra, the cymbal sound, everything. We couldn’t even see where the sound was coming from anymore. At three-quarters of a mile, we had trusties from the jail raking leaves, and they were putting in music requests.'”
Judging from their story (abstract only), the MAD’s sound quality might be high-fidelity enough to be used for music enjoyment in addition to inflicting pain on enemy soldiers, or just plain freaking them out. A music festival probably wouldn’t want to rely primarily on MAD devices for its sound system, but a few sets aimed at the people in the back half of an outdoor even might sound quality. They might also be installed in floors or ceilings of clubs to create various audio zones with less cross-leakage than if conventional speakers ere used.