Specgram and Fourier transform for blog post.

specgram_fourier.py

from scipy.io.wavfile import read, write
import numpy as np
from matplotlib import pyplot as plt


def plotGraph(data, rate):
    """Plot an amplitude - spectrogram graph."""
    norm_data = data.astype('double') / ( 2 ** 15 - 1)
    x_axis = np.arange(len(norm_data)) / rate

    ax = plt.subplot(311)
    plt.plot([2, 2], [0, 22050], 'r-', lw=4)
    Pxx, freqs, t, x = plt.specgram(data, NFFT=512, noverlap=0, Fs=rate)
    ax.set_xlabel('s')
    ax.set_ylabel('Hz')

    ax = plt.subplot(312)
    plt.plot(freqs, list(zip(*Pxx))[88200//512])
    ax.set_xlabel('Hz')

    ax = plt.subplot(313)
    plt.plot(freqs, list(zip(*Pxx))[88200//512])
    ax.set_xlabel('Hz')
    ax.set_yscale('log')

    plt.show()


if __name__ == '__main__':
    rate, data = read('out.wav')
    plotGraph(data, rate)