Mic Array v2.0 recording high pitch noise

I have used the Mic Array v2.0 for a while now. One thing I’ve noticed is that the first channel, i.e. the beamformed channel for ASR, always contains some hight pitch noise. See the attached picture of the spectrogram.

I have tried tuning the parameters but couldn’t get rid of it. Seems it has picked up some interferences.

For the reference, I am using Raspberry Pi 3 for recording. AGC and Noise Suppression are both turned on. Below is a link to the audio file

<LINK_TEXT text=“https://www.dropbox.com/s/zn66l91bich6o … g.wav?dl=1”>https://www.dropbox.com/s/zn66l91bich6oms/mic-array-recording.wav?dl=1</LINK_TEXT>

Any assistance is appreciated.




Further to my problem I’ve done some investigation and believe the high pitch noise comes from the USB. As you can see from the spectrogram the noise has a perfect fundamental frequency at 1kHz and harmonics at multiples of 1kHz. I read some articles with the following explanation:

Any suggestions?