I have created a sine wave of 1000 Hz using
sox -n -r 44100 other_1000Hz.wav synth 1 sine 7000
When I show this spectogram for the MFE buillding block it looks as follows:
So it shows very high energy and also very low energy values around 1000Hz band.
I would not expect these “very low energy values”.
I would expect a single band around 1000Hz with constant high energy value.
FYI: MEL spectogram for same audio fragment in audacity: