I have an audio application that I intended to use a Colibri iMX6S for recording audio. However I recently run a couple of tests and noticed there is what seems to be a hardware noise near 10kHz, and at 650Hz (thou it is less noisy) as shown in the picture (using audacity, and showing the spectrogram).
I have tested this with 3 Colibri iMX6, and all of them have shown the same problem. I am using iris carrier board with all of them.
Note, that I also have several VF61 that do not show this problem. Picture below was taken from an audio recording from a VF61, and what I expect from iMX6 as well.
I have used the exact same setup for both the VF61, and iMX6. I have also tried changing power source, location, nothing worked.
These audios were recorded without any microphone, thou the noise is still there and very visible when using one. So it seems this problem is associated with the hardware.
I am recording using the following command and parameters on the iMX6:
arecord --device=hw:0,0,0 -q -r 48000 -f S16_LE -c 1 -t wav -d 60 “recording.wav”
(I am recording using only one channel and subdevice 0 (left channel)).
Any idea on how to eliminate the noise?