[LAD] Looking for the cause of pulsating noises

[Ralf Mardorf]

Olivier Guilyardi wrote:
> Here is the sample, it's a musical flute and violin recording:
> http://sound.samalyse.org/tapemachine/pulsations.wav
>
> Listen carefully and you will here small pulsations.

Here I didn't need to listen carefully, it's unmistakable. I know this 
kind of noise when doing recordings with anlog consumer cassette 
recorders and cheap microphones and cables.

Listen carefully and you will here this or similar pulsations for the 
sine wave too, perhaps just some background noise, when the sine was 
recorded.

What happens for recordings without microphones?

Ralf