How to write stereo wav files in Python?

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The following code writes a simple sine at frequency 400Hz to a mono WAV file. How should this code be changed in order to produce a stereo WAV file. The second channel should be in a different frequency.

import math
import wave
import struct

freq = 440.0
data_size = 40000
fname = "WaveTest.wav"
frate = 11025.0  # framerate as a float
amp = 64000.0     # multiplier for amplitude

sine_list_x = []
for x in range(data_size):
    sine_list_x.append(math.sin(2*math.pi*freq*(x/frate)))

wav_file = wave.open(fname, "w")

nchannels = 1
sampwidth = 2
framerate = int(frate)
nframes = data_size
comptype = "NONE"
compname = "not compressed"

wav_file.setparams((nchannels, sampwidth, framerate, nframes,
    comptype, compname))

for s in sine_list_x:
    # write the audio frames to file
    wav_file.writeframes(struct.pack('h', int(s*amp/2)))

wav_file.close()
wave wav python
3 Answers

Another option is to use the SciPy and NumPy libraries. In the below example, we produce a stereo wave file where the left channel has a low-frequency tone while the right channel has a higher-frequency tone.

To install SciPy, see: https://pypi.org/project/scipy/

import numpy as np
from scipy.io import wavfile

# User input
duration=5.0
toneFrequency_left=500 #Hz (20,000 Hz max value)
toneFrequency_right=1200 #Hz (20,000 Hz max value)

# Constants
samplingFrequency=48000

# Generate Tones
time_x=np.arange(0, duration, 1.0/float(samplingFrequency))
toneLeft_y=np.cos(2.0 * np.pi * toneFrequency_left * time_x)
toneRight_y=np.cos(2.0 * np.pi * toneFrequency_right * time_x)

# A 2D array where the left and right tones are contained in their respective rows
tone_y_stereo=np.vstack((toneLeft_y, toneRight_y))

# Reshape 2D array so that the left and right tones are contained in their respective columns
tone_y_stereo=tone_y_stereo.transpose()

# Produce an audio file that contains stereo sound
wavfile.write('stereoAudio.wav', samplingFrequency, tone_y_stereo)

Environment Notes

Version Used Python 3.7.1

  • Python 3.7.1
  • SciPy 1.1.0
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