Plot a log amplitude spectrum

log_amp_spectrum.py

import sys
import scipy.fftpack
import scipy.io.wavfile
import numpy as np
import matplotlib.pyplot as plt

if __name__ == "__main__":
    wav_file = sys.argv[1]
    f_s, x = scipy.io.wavfile.read(wav_file)

    N = 2048
    """
        T = N / f_s
        where, T[sec] is window size.
    """
    X = scipy.fftpack.fft(x[:N])
    X = scipy.fftpack.fftshift(X)   # リストの順を自然なものに変更
    log_amp_spectrum = np.log10(np.abs(X))

    freqs = scipy.fftpack.fftfreq(N, d=1/f_s)
    freq_axis = scipy.fftpack.fftshift(freqs)

    plt.plot(freq_axis[freq_axis.size//2:], log_amp_spectrum[freq_axis.size//2:])
    plt.show()