I am trying to figure out the frequencies in a Pulse Code Modulated (PCM) signal. The PCM samples are in .wav files. I am trying to produce a spectrograph of the frequencies in the files. I have coded the Fast Fourier Transform, but that only gives me the coefficients. What should I multiply times the output of the FFT to get the frequencies? Thanks for your help. I have been fumbling through textbooks, but although I have found some great information on how the FFT works, I have not been able to find the last step.