I'm a little bit on a loss at my search for an algorithm due to audio signals.
I'm a sw-engineer with some basis knowledge in math here and there, know how to build and use FFT etc. but with no prof knowledge of dsp in special. So maybe my problem is quite easy to answer for a professional?
OK, my problem:
I have an audio signal and want to know if there is a frequency (or more) that stays for at least a special time. (Of course with some tolerance: "frequency that stays": amplitude doesn't change more than say 3%).
In other words:
If I have a look at the consecutive FFT windows I want to know if there is any frequency that is there for some time with about the same volume.
Yes, you will have guessed, my question is: Is there any interfering signal somewhere in the audio?
(Looking at the spectrogram you see them at first sight... maybe use a visual alg on that?)
I'm sure there will be prof way to find out, rather than to tinker an alg for myself again.