sound.py

import numpy
import scipy.signal

import pygame, pygame.sndarray


def play_for(sample_wave, ms):
    """Play the given NumPy array, as a sound, for ms milliseconds."""
    sound = pygame.sndarray.make_sound(sample_wave)
    sound.play(-1)
    pygame.time.delay(ms)
    sound.stop()


sample_rate = 44100


def sine_wave(hz, peak=8192, n_samples=sample_rate):
    """Compute N samples of a sine wave with given frequency and peak amplitude.
       Defaults to one second.
    """
    length = sample_rate / float(hz)
    omega = numpy.pi * 2 / length
    xvalues = numpy.arange(int(length)) * omega
    onecycle = peak * numpy.sin(xvalues)
    return numpy.resize(onecycle, (n_samples,)).astype(numpy.int16)


def square_wave(hz, peak=8192, duty_cycle=.1, n_samples=sample_rate):
    """Compute N samples of a sine wave with given frequency and peak amplitude.
       Defaults to one second.
    """
    t = numpy.linspace(0, 1, 500 * 440/hz, endpoint=False)
    wave = scipy.signal.square(2 * numpy.pi * 5 * t, duty=duty_cycle)
    wave = numpy.resize(wave, (n_samples,))
    return (peak / 2 * wave.astype(numpy.int16)).astype(numpy.int16)


pygame.mixer.init(channels=1)

# Play A (440Hz) for 1 second as a sine wave:
play_for(sine_wave(440), 1000)

# Play A-440 for 1 second as a square wave:
play_for(square_wave(440), 1000)