We are getting ready to deploy audiomoths for a project in central California to record in the sonic range (sample rate 48 kHz) and have just start to test a few of the units and I have noticed a lot of self noise. Has anyone figured out how to minimize this noise? These units were deployed in Tupperware cases with a goretex cloth sicker over a 15/64" hole. they had the three internal batteries installed ( Duracell AA 1.5V, new, Alkaline). AudioMoth 1.0.0 with the 1.2.0 firmware. We have two models of SD card: SanDisk mobile Ultra 32gd microSD HC I and SanDisk 32gd microSD HC class 2. We put three devices out with gain set at 0, 2 and 4. all three recorded and biological sounds were audible and visible on the spectrograms but there was also a lot of self noise on each (slightly different types of which I have provided examples of two of the devices below). (updated)
Hi, What make and model of batteries and SD card are you using?
I just updated the post above with all the info you requested plus anything else I thought was pertinent.
Here is another view of data from the three units. I have adjusted contrast to optimize viewing
This is noise from the SD card writes. If you have one, try an SanDisk Extreme SD card (these are the red and gold ones - https://www.amazon.co.uk/SanDisk-Extreme-microSDHC-Adapter-Performance/dp/B06XWMQ81P/ref=sr_1_1?keywords=SanDisk+extreme+32GB&qid=1553032186&s=computers&sr=1-1).
Thanks I will try that!