How to convert single output of microphone into multiple values for using fft?
The FFT will process the samples bs time of your analog signal. For 8 consecutive samples in time from your sound file you will get 8 uniformly spaced frequency bins in your FFT ranging from DC up to 7/8 of your sampling rate, and each bin will have a frequency resolution of 1/T Hz where T is the time duration of your 8 samples. I think you will see from that, for your application, you will want a lot more samples (assuming you are interested in seeing more frequencies). Also learn about windowing where you taper the magnitude of your analog signal prior to taking the FFT and how that will effect the dynamic range and frequency resolution.