Ultrasonic Sound Signals
Discussions center on the feasibility of generating and detecting ultrasonic or infrasonic sounds with phone speakers and other hardware, potential health risks from inaudible audio, and countermeasures like interference or detectors.
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Wouldn't these sound waves be below the human hearing threshold (20hz)?
Perhaps the frequencies are below the audible spectrum?
No mention of sound transmission on this or the stackexchange link someone posted.
What counter-measures exist? (e.g. an audio detector listening above 20 kHz?)
Can phone speakers really make sound in ultrasonic range?
WARNING: sounds you can't hear can still damages your ear. DO NOT INCREASE THE VOLUME ON INFRA OR ULTRA SOUNDS BECAUSE YOU CAN'T HEAR THEM
I'd bet a simple loudspeaker with pink noise wouldn't fare worse (as in: that's basically what is helping here, too).
The soundwaves float, not the thing producing them.
Why does it produce sound? Why not infrared or something easily detectable?
The speakers would have to be able to emit ultrasonic waves. I'm pretty sure that you need special hardware for this. (because the researchers themselves used a special ultrasonic emitter, not the speaker of the phone they used).