DSP/Spectrogram.py at master · Baraday3/DSP · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
# import the libraries

import matplotlib.pyplot as plot

import numpy as np


# Define the list of frequencies

frequencies         = np.arange(5,105,5)


# Sampling Frequency

samplingFrequency   = 400


# Create two ndarrays

s1 = np.empty([0]) # For samples

s2 = np.empty([0]) # For signal


# Start Value of the sample

start   = 1


# Stop Value of the sample

stop    = samplingFrequency+1


for frequency in frequencies:

    sub1 = np.arange(start, stop, 1)


    # Signal - Sine wave with varying frequency + Noise

    sub2 = np.sin(2*np.pi*sub1*frequency*1/samplingFrequency)+np.random.randn(len(sub1))


    s1      = np.append(s1, sub1)

    s2      = np.append(s2, sub2)


    start   = stop+1

    stop    = start+samplingFrequency


# Plot the signal

plot.subplot(211)

plot.plot(s1,s2)

plot.xlabel('Sample')

plot.ylabel('Amplitude')


# Plot the spectrogram

plot.subplot(212)

powerSpectrum, freqenciesFound, time, imageAxis = plot.specgram(s2, Fs=samplingFrequency)

plot.xlabel('Time')

plot.ylabel('Frequency')

print(powerSpectrum[[0,1],1])

plot.show()