show impulse response as spectrum (no windowing)

wav2spectrum.py

# -*- coding: utf-8 -*-
"""
Read a 32-bit (!) wave file and plot  frequency response
"""

import numpy as np
import matplotlib.pyplot as plt
import wave
import sys
import os

np.set_printoptions(precision=15, suppress=True)

def freqresponse(b, fs, N):
    Y = np.fft.fft(b, N)
    Ym = np.abs(Y)
    Ydb = 20*np.log10(Ym/Ym.max())
    # Frequency vector
    f = np.arange(N)*fs/N        
    return Ydb, f
    
if __name__ == "__main__":
     
    # filename manipulation
    inputPath = sys.argv[1]
    dirname, filename = os.path.split(inputPath)
    outfilename = os.path.splitext(filename)[0] + '.png'
    outputPath = os.path.join(dirname, outfilename)
    
    # analyze wav file
    wavdata = wave.open(inputPath,'r')
    fs = wavdata.getframerate()
    N = wavdata.getnframes()
    signal = wavdata.readframes(N)
    signal = np.fromstring(signal, 'Int32') 
    Ydb, f = freqresponse(signal, fs, N)
    #Ydb = Ydb * np.blackman(N)
    
    # Plot the frequency response
    plt.clf()
    plt.plot(f, Ydb, 'g')
    plt.grid(True)
    plt.hold(True)
    plt.title(filename)
    plt.xlabel('Frequency [Hz]')
    plt.ylabel('Amplitude [dB]')
    plt.xlim(0, 0.5*fs)
    plt.ylim(-210,10)
    plt.legend()
    plt.savefig(outputPath, bbox_inches='tight')
    plt.close()