
Using Infrasonic Sound to Detect an Intruder - lormayna
http://techcrunch.com/2014/11/03/cocoon/
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th0ma5
A recent art project used ultrasonic waves to jam cellphone microphones. The
idea was to prevent eavesdropping from recorder applications or a compromised,
or otherwise always-on mic.

A side effect of this, and perhaps these devices as well, as depending on the
volume, these effectively create RF interference in a way in the circuit, as
in the electromagnetic signal beyond the mic is changed, and could lead to
unintended side effects such as the inability to speak to 911/999 emergency
services.

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rdrey
I interpreted this design as a microphone only, not something that also emits
sound. I could be totally wrong though.

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th0ma5
Yes, I think you're right.

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jwcacces
My dog does this.

He knows way before I do when someone he knows is walking / driving up the
street

