You have to have a way to mechanically couple the microphone type device to the person's body. What you wan to hear is at a very low level, and would require a lot of amplification. This will be difficult. You will also have the problem with the environmental noise.
The output levels from these piezzo disks is very low. They need some type of force against them in order to generate some output. If is the sensor type, these are not very responsive to sounds. They are designed to pickup vibrations, and changes in mechanical pressure. If you are thinking of any type of power from them, it is going to be only a few microvolts. This level of supply is really useless for any practical means.
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Jerry G.
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"Josh" wrote in message
news:1109724761.839892.179000@g14g2000cwa.googlegroups.com...
I just found out about them a week ago. First Query: Would it be
possible to insert one into someone's clothing (So it wouldn't be
noticable to them) to hear things like subvocalizations or other bodily
noises, etc.? Second Query: What kind of power source do they need?
I've heard some RFID's can run on the power of the human body itself.
Thankis for any replies.
-Josh