I have a problem involving cut-off frequency.
I have a voice message in an audio file .mat which have an eletromagnetic noise. I am trying to recover the original message by applying digital Butterworth filter with MatLab. To this, besides of design the Butterworth filter, also I have to find the cut-off frequency to eliminate all, or partially, the electromagnetic noise.
The picture below shows the Fourier Spectrum of the voice message with the electromagnetic noise. How could I find the cut-off frequency to eliminate the noise? Thanks in advance!
Sampling frequency = 44.8 kHz.