pythonpython-2.7audioscipyspectrogram

Spectrogram of a wave file


I am trying to obtain spectrogram of a wav file in python. But it gives the error:

'module' object has no attribute 'spectrogram'.

Here is the code :

import scipy.io.wavfile
from scipy.io.wavfile import read
from scipy import signal

sr_value, x_value = scipy.io.wavfile.read("test.wav")

f, t, Sxx= signal.spectrogram(x_value,sr_value)

Is there also any way to obtain the spectrogram of a wav file?


Solution

  • Using scipy.fftpack we can plot fft contents as spectrogram.

    ** This is based on my old posting **

    Sample Code Below.

    """Plots
    Time in MS Vs Amplitude in DB of a input wav signal
    """
    
    import numpy
    import matplotlib.pyplot as plt
    import pylab
    from scipy.io import wavfile
    from scipy.fftpack import fft
    
    
    myAudio = "audio.wav"
    
    #Read file and get sampling freq [ usually 44100 Hz ]  and sound object
    samplingFreq, mySound = wavfile.read(myAudio)
    
    #Check if wave file is 16bit or 32 bit. 24bit is not supported
    mySoundDataType = mySound.dtype
    
    #We can convert our sound array to floating point values ranging from -1 to 1 as follows
    
    mySound = mySound / (2.**15)
    
    #Check sample points and sound channel for duel channel(5060, 2) or  (5060, ) for mono channel
    
    mySoundShape = mySound.shape
    samplePoints = float(mySound.shape[0])
    
    #Get duration of sound file
    signalDuration =  mySound.shape[0] / samplingFreq
    
    #If two channels, then select only one channel
    mySoundOneChannel = mySound[:,0]
    
    #Plotting the tone
    
    # We can represent sound by plotting the pressure values against time axis.
    #Create an array of sample point in one dimension
    timeArray = numpy.arange(0, samplePoints, 1)
    
    #
    timeArray = timeArray / samplingFreq
    
    #Scale to milliSeconds
    timeArray = timeArray * 1000
    
    #Plot the tone
    plt.plot(timeArray, mySoundOneChannel, color='G')
    plt.xlabel('Time (ms)')
    plt.ylabel('Amplitude')
    plt.show()
    
    
    #Plot frequency content
    #We can get frquency from amplitude and time using FFT , Fast Fourier Transform algorithm
    
    #Get length of mySound object array
    mySoundLength = len(mySound)
    
    #Take the Fourier transformation on given sample point 
    #fftArray = fft(mySound)
    fftArray = fft(mySoundOneChannel)
    
    numUniquePoints = numpy.ceil((mySoundLength + 1) / 2.0)
    fftArray = fftArray[0:numUniquePoints]
    
    #FFT contains both magnitude and phase and given in complex numbers in real + imaginary parts (a + ib) format.
    #By taking absolute value , we get only real part
    
    fftArray = abs(fftArray)
    
    #Scale the fft array by length of sample points so that magnitude does not depend on
    #the length of the signal or on its sampling frequency
    
    fftArray = fftArray / float(mySoundLength)
    
    #FFT has both positive and negative information. Square to get positive only
    fftArray = fftArray **2
    
    #Multiply by two (research why?)
    #Odd NFFT excludes Nyquist point
    if mySoundLength % 2 > 0: #we've got odd number of points in fft
        fftArray[1:len(fftArray)] = fftArray[1:len(fftArray)] * 2
    
    else: #We've got even number of points in fft
        fftArray[1:len(fftArray) -1] = fftArray[1:len(fftArray) -1] * 2  
    
    freqArray = numpy.arange(0, numUniquePoints, 1.0) * (samplingFreq / mySoundLength);
    
    #Plot the frequency
    plt.plot(freqArray/1000, 10 * numpy.log10 (fftArray), color='B')
    plt.xlabel('Frequency (Khz)')
    plt.ylabel('Power (dB)')
    plt.show()
    
    #Get List of element in frequency array
    #print freqArray.dtype.type
    freqArrayLength = len(freqArray)
    print "freqArrayLength =", freqArrayLength
    numpy.savetxt("freqData.txt", freqArray, fmt='%6.2f')
    
    #Print FFtarray information
    print "fftArray length =", len(fftArray)
    numpy.savetxt("fftData.txt", fftArray)
    

    Sample Plots: enter image description here

    enter image description here