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Recording Setup

A project log for High Performance Audio ADC for Machine Learning

A system that can record high quality audio (24 bit, 48kHz 120db SNR) continuously and unattended outdoors.

filip-mulierFilip Mulier 10/09/2021 at 19:490 Comments
Recorder

Here is a typical setup for recording.  The microphone housing with the ADC and raspberry Pi is on a tripod inside a non-woven bag to reduce wind noise.   I use my phone's hot spot to create a wireless network for the Raspberry Pi and my tablet.  I can then SSH into the Raspberry pi, edit the config script and launch the recording.  I then disconnect and shut down the hot spot.  I found that at high gain levels and during silent parts of the recordings I could hear a rumble or 'burp' sound every 5 seconds.  This turned out to be interference caused by the Raspberry Pi WIFI transmitter searching for a network.  I wrapped copper foil around the microphones and improved the microphone cable layout but it did not help. I also tried reducing the transmit power, but this does not seem to affect the actual power transmitted in the Raspberry pi.  So the current code has the option to automatically shut down the wifi 2 minutes after recording starts to avoid the issue.

I got power usage down to about 60-70mA at 12 volts using a more efficient buck converter, so am able to easily run 48 hours on a 5000mAh 3 cell lithium ion battery.  When the PI is shut down, it uses 20mA at 12 volts.

I've recorded about 30 days worth of recordings so far with this setup.  The most interesting are recordings from before sunset  to after sunrise for nature recordings.

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