I get a repetitive rapid ticking noise in a well-defined band between 52-56 kHz. It comes and goes but mostly it continues for long periods (over 30 mins). Sample rate 250000 - recording just outside my house from sunset through the night. Any ideas what this might be?
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Hello! Just to check, is this the way you notice the noise? Like that continuous band at a low frequency? This was recorded with a medium gain, but it happens to me all the time with any gain I try. Both underwater and in the air. I use a SanDisk Ultra 32 GB and rechargable EBL batteries just fully-charged. Another person is having exactly the same noise.
Hi, If these are a regular 65ms apart, they are due to the SD card write noise. One of the compromises of AudioMoth is placing the microphone and SD card on the same PCB. SD cards often generate significant electrical and mechanical noise due to their high write currents (they have internal capacitors that physically expand and contract with the write current). Some SD cards are better than others and Sandisk Extreme (red and gold) will be better than SanDisk Ultra which is also a bit on the slow side for 250kHz sampling. It will often be more apparent as the batteries discharge as the SD card then causes large voltage drops. It will also be less apparent at 192kHz due to the oversampling that can occur at the lower sample rate. Alex
Just reading some other similar posts and I see it might be to do with SD card writing or batteries? - my card is a SanDisk Ultra 32 GByte and batteries are Energizer rechargeable. Device ID 249BC30461CBBA03 Firmware: 1.8.0