Spectrogram of wav file
How @Pichenettes said, we need more information to help properly

I'll take a guess:

If your Frame Rate are 44100, you will have 1587600 samples for 36 second of audio (36*44100), for the calculation example:

Pxx, freqs, bins, im=pylab.specgram(sound_info, Fs=frame_rate)


pylab.specgram seems use FFT Size = 256 and Overlap = 128 (50%) its give me the follow dimensional array:

floor(1587600 /  128) = 12403 

(128, 12403)

You need set properly FFT Size and Overlap in your souce code.