Electret tape. It stores electical charge rather than magnetic polarization. When the charged tape is wrapped in an outer layer of foil, it forms a really long microphone. I don't know if a practical application was ever developed. Every application I worked on with these novel microphones could be done better using conventional technology. But it was fun working on sound ranging from infrasonic (5 Hz) to ultrasonic (100 kHz).
By the way, 100 kHz sound waves are very directional. They can easily be shot in a narrow beam across a room. But they are also easily deflected by wind.
Most of this acoustics work was done with DARPA money. Your tax dollars at work.
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By the way, 100 kHz sound waves are very directional. They can easily be shot in a narrow beam across a room. But they are also easily deflected by wind.
Most of this acoustics work was done with DARPA money. Your tax dollars at work.
- mark 12-16-2006 12:35 am