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Mecanical or electrical noise ?

Hi everyone,

I got all my recordings with this kind of noise (in picture) on a Hydromoth Firware Basic 1.11.0. We used SD card SanDisk Extreme 64 Go.

Could it be the SD card when is writing? Do you have any recommandations?

Thanks,

3 comments

3 Comments

Alex Rogers

Jun 24

Hi, Can you share one of the WAV files so I can see the time interval between the events. What batteries are you using? There is geneally always some noise from the SD card writes in the AudioMoth and HydroMoth recordings as this is a constraint of having the MEMS microphone mounted to the same PCB. It is more pronounced when the AudioMoth is in a housing and when the battery voltage is low. The noise is a combination of electrical and mechanical noise - both from the SD card and the supply voltage capacitors on the AudioMoth board. Alex

Alexandre MODI

Jun 24

Replying to

Hi Alex,

Thanks for the clarifications! Yes, please find in attachment one WAV file. We used 3 piles AA Energizer lithium.

Alex Rogers

Jun 24

Replying to

Hi, Yes, the noise occurs every 0.5 seconds, which corresponds the 32kB buffer being filled every 0.5 seconds at 32kHz sampling.

The noise is quite pronounced though. Where was the HydroMoth deployed? The temperature is quite low so I wonder if that was affecting the batteries a little. Energiser Lithium should be pretty good at low temperatures and the voltage looks okay.

AudioMoth 2453AC05641FD463

Recorded at 01:30:00 06/05/2025 (UTC) by AudioMoth 2453AC05641FD463 at medium gain while battery was 4.8V and temperature was -2.0C.

GUANO|Version: 1.0

Make: Open Acoustic Devices

Model: AudioMoth

Serial: 2453AC05641FD463

Firmware Version: AudioMoth-Firmware-Basic (1.11.0)

Timestamp: 2025-05-06T01:30:00Z

Original Filename: 20250506_013000.WAV

OAD|Recording Settings: 32000 GAIN 2

OAD|Battery Voltage: 4.8

Temperature Int: -2.0

Alex