Recently, I have configured a system using the AudioMothUSBMic and an Aquarian AS-1 hydrophone and PA-4 Preamplifier to analyze various UW sounds from boat noise, and various cetaceans (whales, dolphins, etc.) using the AudioMoth Live App. So far the only signals I see are when the hydrophone is tapped sufficiently to show spikes on the spectrogram. It appears most of the UW "noise" is muted and doesn't show up on the spectrogram.
It was suggested that another circuit should be added to the system described above. I have not done such yet and waiting for more guidance.
Below is the setup I use. A 9V battery is attached to one end of the wire and the 3.5 mm TRS male is inserted into the AudioMothUSBMic port. A USB cord is connected between the computer and the USB port on the AudioMoth.
Finally, after putting in the 1.5K resistor into the PA4 preamp, I get a much better signal. In fact just barely touching the hydrophone cord and tip generates noise in the spectrogram. In the graphs to follow, I made a clapping noise with my two hands (second image) about 1 foot from the hydrophone tip, then suspended the hydrophone tip in a cup of water, occasionally touching the sides of the plastic cup (third image). The first image is just letting the program run without touching any part of the hydrophone that was out of water. I now want to try and calibrate the hydrophone using some known frequencies. I set the sampling rate at the highest, 384kHz.