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Introduction

I am trying to find peaks in amplitude within a spectrogram I have produced that plots frequency against time and amplitude as the third axis.

I have looked through and attempted to code a solution using scipy.signal.find_peaks_cwt however the official reference guide did not explain what was meant by the widths parameter.

Question:

When finding peaks using scipy.signal.find_peaks_cwt will it return the frequency-time coordinates? If not is there another library or method to use to return the coordinates of local maxima?

What is the widths parameter within scipy.signal.find_peaks_cwt?

As the scipy.signal.find_peaks_cwt deals with arrays why do you still need to plot a spectrogram in order to find local maxima?

Here is the code i have been using to create the spectrogram:

    import numpy as np      
    import matplotlib.pyplot as plt 
    import scipy.io.wavfile     
    from scipy import signal

    def create_spectrogram(audio):
        rate, data = scipy.io.wavfile.read(audio)        
        data_1D = data.flatten()
        plt.specgram(data_1D, NFFT = 64, Fs = 64, noverlap=32)  
        plt.savefig("melody")  
        plt.show()      


    if __name__ == '__main__':
        audio = "melody.WAV"        
        create_spectrogram(audio)

Here is the outputted Spectrogram:

Here is the outputted Spectrogram:

Links: scipy.signal.find_peaks_cwt reference guide: https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.signal.find_peaks_cwt.html

Daanish Karim
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  • Please read how to create a [mcve] and add the missing information to your Post by editing it :) If you haven't read [ask] yet i recommend to do so :) I highly recommend to follow the 2 guides i linked as the people on SO are more likely to answer questions when the posts follow these guides. What i'm missing in particular is - What have u tried so far? What errors/problems do you face? Do you may have codesnippets that show what you tried so far? – Tobias Theel Jan 06 '18 at 17:53
  • `find_peaks_cwt` is for 1-D array. If you want to find local peaks in your 2-D spectrogram, please read this: https://stackoverflow.com/questions/3684484/peak-detection-in-a-2d-array – Gerges Jan 06 '18 at 22:34

1 Answers1

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Could you please give a bit more information as to how exactly is your data stored in your code? Is it a numpy array, a scipy.signal.spectrogram or simple python lists? A snippet of code would help a lot in trying to help you find a good solution.

For the moment the only "easy" way I would suggest is to have a look at numpy.amax(), choosing wisely the value given to the axis parameter, should get you the maximum you are looking for.

domochevski
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