It seems that the MFE spectogram shown in Edge Impulse studio is limited to 8000Hz.
This makes sense if audio is recorded at 16000Hz, but I am recording at 44100Hz.
So in case of audio fragments recorded at 44100Hz, it would be good that the spectogram goes up to 22050Hz instead of 8000Hz.
FYI here the output for sine wave of 7000Hz recorded at 44100Hz.
same sine wave in audacity:
FYI the command to create the sine wave:
sox -n -r 44100 other_1000Hz.wav synth 1 sine 7000