Absolute Gain levels for AudioMoth 1.2.0
Hello,
I have found many (contradictory) estimations of the relative or absolute gain levels of the 5 modes (0-4). However, as the sensitivity of the 1.2 device version is 20 dbv lower (-38), I assume the gain levels will be different. I need it in order to calculate the true true SPL values of jackals I recorded with the AudioMoth. Here, for instance, two difference sets of gain absolute levels are given (for the 1.1 version:
https://bioacoustics.stackexchange.com/questions/1659/amplification-gain-of-audiomoth
and the article on the Hardware from 2019 gives a shorter range of values (ranging from +27 to +33 Db): https://www.hardware-x.com/article/S2468-0672(19)30030-6/fulltext.
Thank you for your great work,
Zacharie
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Hi Zacharie, This table shows the sensitivity of the microphones and the gain of the microphone pre-amp (for AM 1.2.0) plus the gain of all the other stages.
https://docs.google.com/spreadsheets/d/1QrBwOq7biyI58oH25b-Y-pc5MU42wlQMzgbKro87xVc/edit?usp=sharing
To work out the SPL of the sound from the WAV file, you also need to know that the ADC reference is a peak-to-peak signal of 2.5V which corresponds to a full-scale WAV output of -1 to 1. I assume that you'd then need to compute the RMS of the sound from the WAV file, and then work backwards through the various stages to get the equivalent db SPL value.
All the numbers for the AudioMoth 1.2.0 hardware is in this application note: https://github.com/OpenAcousticDevices/Application-Notes/blob/master/Using_AudioMoth_with_Piezoelectric_Hydrophones_and_Contact_Microphones/Using_AudioMoth_with_Piezoelectric_Hydrophones_and_Contact_Microphones.pdf Note that the sensitivity value is from the microphone datasheet so you'd also have to potentially account for the loss from the acoustic vent. The Gore vent datasheet suggests that might be 1 or 2 dB SPL: https://groupgets-files.s3.amazonaws.com/AudioMoth/GORE-Acoustic-Vent-GAW334-Datasheet-en.pdf
Alex