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

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    Acoustic Design
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Discussion Overview

The discussion revolves around the feasibility of creating a high-frequency microphone using a laser and reflective material, specifically targeting frequencies up to 100 kHz. Participants explore various methods of detecting sound through optical means and the properties of materials that could be utilized in this application.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using a laser bounced off reflective material to detect high frequencies, considering methods such as pulse width modulation and Doppler shift for sound detection.
  • The initial poster expresses uncertainty about the material properties needed, including thickness, surface area, tension, and potential resonant frequency.
  • Another participant shares links to patents and existing acoustic sensors that operate at similar frequencies, suggesting these resources may provide useful insights.
  • Additional resources on optical detectors are provided, indicating various approaches that could be relevant to the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific material properties or methods for achieving the desired frequency range, and multiple approaches are suggested without resolution.

Contextual Notes

The discussion lacks detailed exploration of the assumptions regarding material properties and the specific conditions under which the proposed methods would be effective. The feasibility of the proposed techniques remains uncertain.

Who May Find This Useful

This discussion may be of interest to those exploring innovative microphone designs, particularly in the context of high-frequency sound detection and optical sensing technologies.

Raven Luni
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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?
 
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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
 
Last edited by a moderator:
Excellent information - thanks :)
 

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