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There are acoustic glitches in my recordings, and I would like to know the cause of the sound anomaly and possible fixes.

This is what our spectrogram looks like:

enter image description here

And here are the example recordings from these two malfunctioning microphones: https://drive.google.com/drive/folders/1ZQINiZbWgIkgOtGfrsTq_WeOeHugRS_b?usp=sharing

In words:

it resembles and sounds like the noise we have from outdoors recordings when wind is present but we don't use a windscreen: the noise is concentrated in the lowest frequencies. Also, the noise can slowly or suddenly kick in, but its presence is totally unpredictable and sporadic (which complicates things).

Technical details:

We have a field team that is recording natural soundscapes in the tropics using SM2 Song Meters (Wildlife acoustics Inc.) and simple, self-built, open-design microphones after this article. The microphones essentially only consist of a MEMS microphone (Knowles, Invensense), have a SNR of 62-70 dB, a sensitivity of -36 dB, and we set the recorder amplification to 48 dB.

Context:

Unfortunately the field team has limited capacity for testing the microphones extensively and for sending me data remotely, so I am relying on the internet to investigate the issue. However, it was a bit more difficult than I thought, because people talk and mix up "hissing" noise (what is that?), "white" noise (this is clearly defined but not what we have here), or "static" noise (vaguely defined), and sample recordings are very rarely provided.

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  • It sounds somewhat akin to Motorboating but I couldn't say for sure. I've known it happen if mics get damp [eg in humid conditions] but idk anything about how to fix it - I've always just sent them to the lab for the boffins to sort out ;)
    – Tetsujin
    Sep 9 at 6:58
  • To my ears it sounds like a failing semiconductor. Like an op amp going out.
    – Tom
    Sep 15 at 3:37

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