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Questions about hydrophones

Discussion in 'General Electronics' started by TIMO PARRU, Feb 14, 2004.

  1. TIMO PARRU

    TIMO PARRU Guest

    If this is wrong group to ask about hydrophones, let me know what is better.

    1) In all DIY projects hydrophones are made based on piezoelement. Why
    piezo?
    2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
    (3-4mm) discs and put o-ring inbetween.
    - How thickness of plexiglass affects sound quality and performance?
    - How air volume inside 'sandwich' affects sound quality and
    performance?
    3) What would be good link to find more info?

    /timo
     
  2. Robert Baer

    Robert Baer Guest

    Nickel and alloys can also act as transducers; wire in some power
    potentiometers can be used for starters...
     
  3. Chris

    Chris Guest

    Piezo has a good linear response and doesn't mind being potted
    and/or can stand getting wet. They also don't mind the static
    water pressure that you get from depth.

    If you have air in the gap, you'll get a bit of distortion and a poor
    response. Best method is to 'pot' the crystal or piezo in something with a
    Rho-C roughly the same as water to minimize the impedance mismatch. For
    DIY stuff, silicon rubber is probably just fine.

    Take a small waxed paper cup, hang the wired piezo (and amplifier circuit
    if you want) in the middle and fill with silicon. Peel cut off afterward.
    A cheap caulking gun tube of clear silicon goes for $2 at Walmart.

    -Chris
     
  4. TP

    TP Guest

    Is that true that piezo has a good linear response? The piezos Radioshack
    sells
    has about 30dB variation over range when using it to produce sound.
     
  5. N. Thornton

    N. Thornton Guest

    Thats frequency response, which is a different thing to linearity.

    Regards, NT
     
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