Said another way: If I see a value in my spectrogram of -250 dB is that a number which could actually be recorded by an AudioMoth (at a given frequency).

I am barely a novice at audio recording and this is all interesting, but it is going to take me some time to digest. I will try to motivate my reason for asking a bit more below (hopefully it helps): I am simply trying to understand when is signal really signal. For example, if I build a spectrogram which has values in dB at what level can the AudioMoth produce a value that is real. If it varies in the frequency domain, that is fine. I simply need to throw away as much data as I can from our recordings.