Python: Frequency Modulation with NumPy
In this video I show how generate frequency modulation from a Python NumPy array.
The code for the tutorial is:
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| import numpy as np | |
| from scipy.io.wavfile import write | |
| import sounddevice as sd | |
| import time | |
| # Samples per second | |
| sps = 44100 | |
| # Duration | |
| duration_s = 5.0 | |
| # ac: amplitude of the carrier. Should be kept at 1.0 in this script | |
| # you would modify it if you were micing it with, or modulating other, | |
| # waveforms. | |
| # carrier_hz: Frequency of the carrier | |
| # fm_hz: Frequency of the frequency modulator | |
| # k_p: deviation constant | |
| carrier_amplitude = 1.0 | |
| carrier_hz = 440.0 | |
| fm_hz = 220.0 | |
| k = 25.0 | |
| # Our final waveform is going to be calculated as the cosine of carrier and | |
| # frequency modulated terms. | |
| # First, define our range of sample numbers | |
| each_sample_number = np.arange(duration_s * sps) | |
| # Create the term that create the carrier | |
| carrier = 2 * np.pi * each_sample_number * carrier_hz / sps | |
| # Now create the term that is the frequency modulator | |
| modulator = k * np.sin(2 * np.pi * each_sample_number * fm_hz / sps) | |
| # Now create the modulated waveform, and attenuate it | |
| waveform = np.cos(carrier + modulator) | |
| waveform_quiet = waveform * 0.3 | |
| # Adjust amplitude of waveform and write the .wav file. | |
| waveform_integers = np.int16(waveform_quiet * 32767) | |
| write('fm-out.wav', sps, waveform_integers) | |
| # Play the waveform out the speakers | |
| sd.play(waveform_quiet, sps) | |
| time.sleep(duration_s) | |
| sd.stop() |
