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I am looking for a very cheap way to record sound underwater. I am mostly interested in recording low frequencies (i.e. ~ [10 - 5000] Hz). I have seen a few papers on MEMS technology to record sound underwater (e.g. Xu et al 2018, Travaglione et al. 2018) but was wondering if anyone here used MEMS microphones to record underwater sounds from whales/fish/invertebrates?

I have seen that the VM1000 piezo MEMS microphone from Vesper can go underwater but is limited to a depth of a few meters. Are there any other MEMS microphones out there that could work underwater?

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  • $\begingroup$ The HydroMoth (underwater version of AudioMoth) is a recent example: MEMS microphone, up to 60m depth claimed groupgets.com/campaigns/1048-hydromoth/show $\endgroup$
    – Dan Stowell ♦
    Feb 3 at 12:02
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    $\begingroup$ Thanks @DanStowell. I am aware of the HydroMoth which is essentially a MEMS microphone in a pressure case. I am more looking for a sensor that can measure directly in the water. $\endgroup$
    – Xavier Mouy
    Feb 3 at 13:36
  • $\begingroup$ Do I understand correctly that you only want to record sound and measuring the levels is not that important? $\endgroup$
    – Mirko Mustonen
    Feb 4 at 9:45
  • $\begingroup$ Yes, what I am ultimately wanting to do is having a low-cost compact array to measure TDOA and do localization. Having acurate levels would be nice too, but not at the top of my priority list. $\endgroup$
    – Xavier Mouy
    Feb 4 at 14:49

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Three Years ago Valentina Cafaro presented a poster at EGU (European Geoscience Union) with some performance figures for a Electret microphone

relative link to download poster is EGU 2020 presentation: D2377 | EGU2020-6746

It uses a Electret microphone with a Teensy MCU/audioboard acquisition system. While not a MEMS microphone, conclusions could be similar and comparing Electret with MEMS would be interesting.

Edit: The trick is to pot the microphone in Resin/Polyurethan, but replacing the air cavities with oil or alcohol (to compensate pressure but let microphone transducer (membrane) still react to sound)

IAW: one question is if the air-chamber in mems that is needed for microphone can be filled with, say alcohol, or not. If not, the presence of air in hydrophone limits the depth rating. If yes, then one would like to know how much the sensitivity is decreased.

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