Can a Laser and Reflective Material Create a High-Frequency Microphone?

[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 don't 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 don't 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/techzone/sensors/resources/articles/ultrasonic-mems-sensor-spm0404ud5.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/fibre-optic-hydrophones

www.ece.msstate.edu/.../ans200-01-2011_04_23_19_55_40.pdf

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

 

[alphy]

Hello,

Thank you for sharing your interesting idea for creating a microphone capable of picking up high frequencies using a laser and reflective material. It sounds like a unique approach that could potentially yield promising results. In terms of the material and its properties, it would be important to consider factors such as the reflectivity of the material, its ability to vibrate at high frequencies, and its durability. The thickness, surface area, and tension of the material would also play a role in its performance as a diaphragm. It is possible that there could be a resonant frequency for the material, but this would likely depend on the specific properties of the material and the design of the diaphragm. Overall, it is difficult to say for certain whether this approach would be successful without further experimentation and analysis, but it certainly seems like a promising avenue to explore. Best of luck with your research and experimentation!