CoCalc -- sounds.py

Path: examples/think-dsp/code / sounds.py
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"""This file contains code used in "Think DSP",
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by Allen B. Downey, available from greenteapress.com
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Copyright 2014 Allen B. Downey
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License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html
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"""
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from __future__ import print_function, division
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import thinkdsp
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import thinkplot
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FORMATS = ['pdf', 'eps']
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def plot_tuning(start=7.0, duration=0.006835):
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    """Plots three cycles of a bell playing A4.
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    start: start time in seconds
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    duration: float
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    """
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    period = duration/3
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    freq = 1/period
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    print(period, freq)
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    assert abs(freq - 438.917337235) < 1e-7
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    wave = thinkdsp.read_wave('18871__zippi1__sound-bell-440hz.wav')
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    segment = wave.segment(start, duration)
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    segment.normalize()
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    thinkplot.preplot(1)
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    segment.plot()
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    thinkplot.Save(root='sounds1',
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                   xlabel='Time (s)',
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                   axis=[start, start+duration, -1.05, 1.05],
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                   formats=FORMATS,
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                   legend=False)
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def plot_violin(start=1.30245, duration=0.00683):
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    """Plots three cycles of a violin playing A4.
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    duration: float
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    """
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    period = duration/3
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    freq = 1/period
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    print(period, freq)
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    assert abs(freq - 439.238653001) < 1e-7
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    wave = thinkdsp.read_wave('92002__jcveliz__violin-origional.wav')
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    segment = wave.segment(start, duration)
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    segment.normalize()
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    thinkplot.preplot(1)
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    segment.plot()
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    thinkplot.Save(root='sounds2',
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                   xlabel='Time (s)',
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                   axis=[start, start+duration, -1.05, 1.05],
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                   formats=FORMATS,
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                   legend=False)
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def segment_violin(start=1.2, duration=0.6):
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    """Load a violin recording and plot its spectrum.
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    start: start time of the segment in seconds
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    duration: in seconds
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    """
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    wave = thinkdsp.read_wave('92002__jcveliz__violin-origional.wav')
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    # extract a segment
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    segment = wave.segment(start, duration)
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    segment.normalize()
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    # plot the spectrum
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    spectrum = segment.make_spectrum()
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    thinkplot.preplot(1)
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    spectrum.plot(high=10000)
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    thinkplot.Save(root='sounds3',
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                   xlabel='Frequency (Hz)',
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                   ylabel='Amplitude',
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                   formats=FORMATS,
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                   legend=False)
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    # print the top 5 peaks
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    peaks = spectrum.peaks()
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    for amp, freq in peaks[:10]:
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        print(freq, amp)
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    assert abs(peaks[0][0] - 3762.382899) < 1e-7
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def mix_cosines():
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    """Plots three periods of a mix of cosines.
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    """
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    # create a SumSignal
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    cos_sig = thinkdsp.CosSignal(freq=440, amp=1.0, offset=0)
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    sin_sig = thinkdsp.SinSignal(freq=880, amp=0.5, offset=0)
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    mix = sin_sig + cos_sig
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    # create a wave
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    wave = mix.make_wave(duration=1.0, start=0, framerate=11025)
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    print('Number of samples', len(wave))
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    print('Timestep in ms', 1000 / wave.framerate)
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    assert len(wave) == wave.framerate
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    # select a segment
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    period = mix.period
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    segment = wave.segment(start=0, duration=period*3)
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    # plot the segment
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    thinkplot.preplot(1)
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    segment.plot()
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    thinkplot.Save(root='sounds4',
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                   xlabel='Time (s)',
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                   axis=[0, period*3, -1.55, 1.55],
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                   formats=FORMATS,
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                   legend=False)
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def main():
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    plot_tuning()
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    plot_violin()
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    segment_violin()
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    mix_cosines()
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if __name__ == '__main__':
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    main()
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