Photo: A Long Range Acoustic Device (LRAD ) is being used here to send a warning from the USS Blue R

The piezoelectric transducers (gray circles) in the directional speaker produce two ultrasonic waves (red and blue), both of which are at frequencies way too high to hear). The transducers pump out the waves in a focused column (like the light in a flashlight beam). The waves are actually modulated (like radio waves) and travel as one wave, but it's simplest to imagine them as two quite separate waves.
When the two waves hit something (or someone), they slow down and demodulate, producing a new wave (green) whose frequency is much lower equal to the difference in frequencies between the two original last minute charter travel specials from detroit waves. This is a wave you can hear.
Photo: A Long Range Acoustic Device (LRAD ) is being used here to send a warning last minute charter travel specials from detroit from the USS Blue Ridge to a small, incoming craft during an attack drill. Note how you have to swivel the LRAD and point it in the direction you want the sound to go, just like a flashlight. Photo by Tucker M. Yates courtesy of U.S. Navy .
US patent #7,343,017: System for playback of pre-encoded signals through a parametric loudspeaker system : If you want the ultimate, technical explanation of how parametric, directional, ultrasound speakers work, this patent is for you. It's very detailed and complex, but it's the definitive last minute charter travel specials from detroit explanation!
Woody Norris: Inventing the next amazing thing : In this 15-minute TED talk from 2009, one of the pioneers of directional last minute charter travel specials from detroit sound explains (sort of) how the invention works and gives a demonstration to a studio audience. He also describes his life as a self-taught last minute charter travel specials from detroit inventor and some of the other inventions he's develoiped.
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