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This tutorial explains how we can plot spectrograms in Python using matplotlib.pyplot.specgram()the and methods.scipy.signal.spectrogram()

We can get detailed information about the signal strength through the spectrum graph. The darker the color of a point in the spectrum graph, the stronger the signal at that point.

Use matplotlib.pyplot.specgram()the method to draw a spectrum

matplotlib.pyplot.specgram(x,
                           NFFT=None,
                           Fs=None,
                           Fc=None,
                           detrend=None,
                           window=None,
                           noverlap=None,
                           cmap=None,
                           xextent=None,
                           pad_to=None,
                           sides=None,
                           scale_by_freq=None,
                           mode=None,
                           scale=None,
                           vmin=None,
                           vmax=None, *,
                           data=None,
                           **kwargs)

Example: matplotlib.pyplot.specgram()Plotting a spectrum using the method

import math
import numpy as np
import matplotlib.pyplot as plt

dt = 0.0001
w = 2
t = np.linspace(0, 5, math.ceil(5 / dt))
A = 20 * (np.sin(3 * np.pi * t))

plt.specgram(A, Fs=1)
plt.title("Spectrogram Using matplotlib.pyplot.specgram() method")
plt.show()

It creates a spectrogram matplotlib.pyplot.specgram()for the function using the method . The parameter in this method represents the sampling frequency.A=20sin(3*np.pi*t)fs

Use scipy.signal.spectrogram()the method to draw a spectrum

import math
import numpy as np
import matplotlib.pyplot as plt
from scipy import signal

dt = 0.0001
w = 2
t = np.linspace(0, 5, math.ceil(5 / dt))
A = 2 * (np.sin(1 * np.pi * 300 * t))

f, t, Sxx = signal.spectrogram(A, fs=1, nfft=514)
plt.pcolormesh(t, f, Sxx)
plt.ylabel("Frequency")
plt.xlabel("Time")
plt.title("Spectrogram Using scipy.signal.spectrogram() method")
plt.show()

It uses the method to create a spectrogram scipy.signal.spectrogram()for the function . The parameters in this method represent the sampling frequency and represent the length of used .A=2sin(300*np.pi*t)fsntftFFT

This method returns three values f, , tand Sxx. frepresents the sampling frequency array, trepresents the sampling time array, and Sxxrepresents Athe spectrum graph of .

This method does not generate a spectrogram of the input signal. We can use matplotlib.pyplot.colormesh()to generate a graph.