I recently did a four-night deployment and checked on it this morning to find my AudioMoth sitting in some water. (Bucket covered in plastic wrap, AudioMoth in ziplock bag but not fully closed because I was using an external mic, AudioMoth and ziplock wrapped in more plastic wrap.) Rainwater found its way in nevertheless. I guess I was a dummy and should have kept the AM elevated off the base of the bucket, among other steps that in retrospect seem obvious.
Anyway, it ran on schedule and wrote to the SD card cleanly until the night after the rain, when it ran on schedule but wrote with all kinds of noisy spikes. It would have been sitting in some water for about 36 hours by that point. I removed the batteries, let the AM sit for a while, then dried it out with a warm (not hot) hair dryer. That's when I confirmed the SD card was fine, the scheduling was fine, and the USB is fine -- it can execute the flash, config, and time apps. But I tested it this morning on Default both with and without the external mic. It runs for the correct amount of time per the resulting file, but the files themselves are almost entirely silent. (Not perfectly silent...just the faintest of noise, of a level one might expect of device noise.)
I removed the batteries and put the AM in a closed ziplock with a desiccant bag. Is there anything else I should be doing or checking?
Edited to add: When I set the toggle to Default, the red LED blinks rapidly without a break.
The internal MEMS mic will most likely be permanently damaged due to the water exposure. Is the silent noise present when using the external mic as well?