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Discussion in 'General Electronics Discussion' started by B3n4, Jun 22, 2013.

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  1. B3n4


    Jun 22, 2013
    Is there a device that you can record a noise, and when the noise is heard it creates an action.

    In this instance I want it to turn a motor.

    Any ideas?

  2. duke37


    Jan 9, 2011
    Audio amplifier
    Level detector
    Time delay
    Switch (transistor, fet, SCR or relay)
  3. BobK


    Jan 5, 2010
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    Nov 28, 2011
    You want to be able to record an arbitrary noise, and when the unit hears the same noise, it performs the action?

    Do you want it to detect that noise on top of any other background noise? (Hint: the correct answer is no, unless you have a LOT of computing power available.)

    The Clapper that Bob mentioned is one way of detecting a sound with specific characteristics - a short burst with a lot of high-frequency content. It works because it's not TOO specific. Any signal with a fairly short duration (ignoring reverberations) and a lot of high-frequency content will trigger it.

    If you want a device that can distinguish the spoken words "blue" and "grey", you can't use any simple trick like that. You need speech recognition software.

    Anything in between is a grey area. It depends on what type of sound you want to detect, and what you want to reject.

    For example if the sound is always at a specific frequency, you can use a filter to identify it. If it has a specific volume or frequency cadence, you may be able to detect that. But it's not simple.

    Recording a sound and trying to match it by comparing on a sample-by-sample basis is not really workable unless the sound is always generated, and received by the microphone, with exactly the same (or almost exactly the same) waveform every time.
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