Acoustic Diaphragm Design

Raven Luni

Greetings,

I've been looking for a way to create a microphone capable of picking up high frequencies (up to about 100kHz). Electrets dont tend to go that high and piezo crystals even detuned will only give a limited band.

I had the idea of bouncing a laser off a sheet of reflective material. The light can either be picked up directly, by pulsing the beam with a square wave and taking the phase shift as a form of pulse width modulation, or with a sine wave and using the doppler shift (I'll have fun experimenting with all these methods).

What I dont have any clue about is the material and what properties it should have. What kind of thickness, surface area, tension etc. would I need? Would there be a resonant frequency? Is it even possible for the frequency range in question?

Bobbywhy

Raven Luni, Welcome to Physics Forums! 

You may see this patent, which detects acoustic frequencies up to 100 kHz:
http://www.google.com/patents/US5146083

Here is a ready-made acoustic sensor you may learn from:
http://www.digikey.com/us/en/techzon...pm0404ud5.html

Raven Luni

Excellent information - thanks :)

Bobbywhy

Just in case you have missed these, here are a few more examples of different kinds of optical detectors:
http://www.acoustics.co.uk/products/...ic-hydrophones

http://www.ece.msstate.edu/.../ans20...3_19_55_40.pdf

http://en.wikipedia.org/wiki/Fiber_optic_sensor