Hey! I want to measure wind induced ambient noise levels in dB in forest habitats with AudioMoth to analyze the distribution of frequencies (I am mainly interested in the spectrum 500Hz - 4kHz). Do I need an external microphone, compatible with a common sound pressure calibrator (eg. 94dB at 1kHz) or is it possible to calibrate the built-in microphone, as well? What else do I have to consider?
Thanks for your support,
Vincent
Hi Silvy,
I'll try my best to answer these for you.
(i) the sensitivity of the acoustic transducer, which defines how much voltage is generated per unit of sound pressure.
The MEMS mic on AudioMoth 1.1.0 has a sensitivity of -18 dBV/Pa, this is measured when used together with the MEMS output amplifier set to a gain of 10. Here is the MEMS mic data sheet for your reference.
(ii) the amount of additional voltage gain applied by the pre-amplifier.
At the mid gain setting this is 15, below are the gain values of the other gain settings corresponding to the radio buttons in the AudioMoth Configuration App.
Gain
0 Min 4.33
1 7
2 Med 15
3 25.1
4 Max 30
(iii) the ADC input voltage which corresponds to the maximum amplitude that can be represented in the audio files.
On AudioMoth 1.1.0 the full 16-bit 0 to 65535 amplitude range corresponds to 0V to 3.3V.
I hope this helps,
Andy