I have downloaded a discrete time signal called pcm.mat file in order to amplify it with a second order IIR filter. Sampling rate for the signal is 8kHz. I used SPTool in MatLab to get the Spectra of the signal. I need to determine the frequency of the signal to is to be amplified. One problem, I can't tell and don't know what peak or minima to chose and amplify. Can anyone please help? Thanks.