
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!

Identifying resonant frequencies in various objects

  1. Aug 26, 2010 #1

    I was wondering if someone would be kind enough to help me with a project I have at the moment.

    Here is the scenario;

    I am playing various tones through a speaker system at a fridge and I need to be able to detect which of the tones make the fridge resonate.

    I have been using a flat microphone taped to the fridge but that seems to be showing me nothing more than its own best frequency response.

    What would be a more sensitive/suitable way to measure the vibrations in the fridge.

    I would like to display the measurement signal on an oscilloscope

    Thanks in advance to anyone who can help.

  2. jcsd
  3. Aug 26, 2010 #2
    An accelerometer attached to the fridge will pick-up the vibrations while being quite insensitive to the sound waves coming though the air.
  4. Aug 26, 2010 #3
    Thank you, that sounds good.

    Any particular one you think would be good? Can they be outputted to an oscilloscope.

  5. Aug 27, 2010 #4
    When I was a teenager, I built an incredibly sensitive microphone that picked up vibrations from a surface without being affected by sound in the air. (It was really good at picking up conversations in the next room!)

    All it was, was a piece of graphite rod extracted from a dry cell balanced on a pivot slightly off centre so that one end rested on another piece of graphite rod.

    Very slight movements of the rods caused pressure changes at the contact points giving a change in conduction. A simple battery supply and a pair of headphones (no amplification) were all it took to make it work.