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I bought a pack of 5 MAX4466 microphones on amazon, and would need to use them to detect when a plate is hit by a bullet. There are 4 plates, each one with a microphone glued to the back. The bullet speed and the speed of sound are very similar, thus the microphone needs to be very tollerant to loud noises. Ideally, the one attached to the plate saturates the output, while the others hearing just the noise of the gun keep a lower value. Unfortunately these mics saturate even with a handclap and even adjusting the gain did not bring any good result.

I also tried other models, but they all have the same problem, they are not designed for noises that loud.

Is there a way (for example attaching a potentiometer parallel to the mic?) that allows me to decrease the sensitivity of the microphone?

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  • \$\begingroup\$ You've tried taking the gain all the way down? You could try an electret on its own without a pre-amplifier? \$\endgroup\$
    – pjc50
    Commented Jul 15, 2021 at 16:18
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    \$\begingroup\$ That makes no sense. MAX4466 is a mic amplifier chip, not a microphone. Would you be more specific what exactly you bought and did it come with datasheet or manual (highly unlikely since you bought it from Amazon and are asking here, so you may have to reverse-engineer the schematics yourself to modify it). \$\endgroup\$
    – Justme
    Commented Jul 15, 2021 at 16:18
  • \$\begingroup\$ @Justme here it is: amazon.it/… there was no datasheet included \$\endgroup\$
    – sharkyenergy
    Commented Jul 15, 2021 at 16:24
  • \$\begingroup\$ @pjc50 yes, already tried taking it all the way down.. still very far away from what I need \$\endgroup\$
    – sharkyenergy
    Commented Jul 15, 2021 at 16:25
  • \$\begingroup\$ try using optical detection instead of audio detection ... a reflective surface on the back of plate (piece of silver mylar or aluminum foil) ... LED and photo-transisor arranged as an optocoupler \$\endgroup\$
    – jsotola
    Commented Jul 15, 2021 at 17:01

2 Answers 2

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Frankly, I doubt it. You may be able to adjust the gain, but when you're looking at a shockwave, it will probably challenge the physical limits of travel of the electret diaphragm.

Since you're attaching it to the plate directly, you might consider trying out some piezo sensors. You can probably find some with a range that would differentiate between a hit and a shockwave. If it was me, I'd be tempted to experiment with ceramic caps to use their microphonic variation to detect impacts.

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  • \$\begingroup\$ Thank you very much. Do these piezo sensors work like a microphone? I mean, do they have an analog out, or are they just simple piezoelectric discs that need the circuit? \$\endgroup\$
    – sharkyenergy
    Commented Jul 15, 2021 at 16:27
  • \$\begingroup\$ The datasheet for the MAX4466 preamp is available on Google. Two resistors set its gain. I think that any microphone type will be saturated by the very loud sound from a bullet hitting a nearby plate. \$\endgroup\$
    – Audioguru
    Commented Jul 15, 2021 at 16:46
  • \$\begingroup\$ @Audioguru do you think that removing the microphone from the circuit and replacing it with a piezo disk could work? \$\endgroup\$
    – sharkyenergy
    Commented Jul 15, 2021 at 16:51
  • \$\begingroup\$ I have never used a piezo as a knock sensor. If its load is a high resistance then its output voltage can be high enough to zap an electronic circuit but with a low resistance load its output voltage is reduced. Try it when measuring it. \$\endgroup\$
    – Audioguru
    Commented Jul 16, 2021 at 18:51
  • \$\begingroup\$ Just as update, i just tried the piezo disks with a 100K potentiometer parallel and it works great. i took small piezos (15mm) to make it less sensitive to noise, it reacts very well when it is hit, but has almost no reaction even to extreme loud noises. thank you very much \$\endgroup\$
    – sharkyenergy
    Commented Jul 18, 2021 at 9:39
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Embed the sensors in foam. Experiment until you get the sensitivity you need.

Alternatively, instead of microphones use accelerometers. You would need to get them with a big range, like +/-10g, but you will be able to buy them with low enough sensitivity.

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