Iterated rippled noise

irn.py

import numpy as np
import brian
import brian.hears as hears

def irn(dur, f, g, n, method='s'):
    """Generate IRN with a duration dur in seconds, a pitch at f (either a
    single value for a flat pitch, or an iterable for a contour) in Hz, a gain
    of g (-1 <= g <= 1) and n iterations. Since this is done in the time
    domain, processing time gets longer with larger n."""
    x = hears.whitenoise(dur * brian.second) #input signal
    y = np.ravel(x)
    y0 = np.ravel(x) #for irno
    if hasattr(f, '__iter__'):
        f = np.array(f)
        delay = np.array(np.round(1/f * x.samplerate), dtype=int)
        if len(delay) != len(y):
            raise Exception('len(f) should be %i, not %i' %(len(y),len(delay)))
    else:
        delay = [int(1/float(f) * float(x.samplerate))] * len(y)
    for i in xrange(n):
        if method == 's':
            y = [y[t] + g*y[t-delay[t]] for t in xrange(len(y))]
        elif method == 'o':
            y = [y0[t] + g*y[t-delay[t]] for t in xrange(len(y))]
        else:
            raise Exception("IRN method not understood: should be 's' or 'o'")
    return hears.Sound(np.array(y) / np.max(y))

def main():
    dur, f, g, N = 1, 200, 1, [0, 4, 8, 16, 32, 64]
    for n in N:
        if not n:
            sound = irn(dur, f, g, n, 's')
        else:
            sound = hears.sequence(sound, irn(dur, f, g, n, 's'))
    sound.play(sleep=True)
    sound.save('IRN_increasing_n.wav', normalise=True)
    dur, f = 2, np.linspace(100, 400, 88200)
    sound = irn(dur, f, g, n, 's')
    sound.play(sleep=True)
    sound.save('IRN_increasing_f.wav', normalise=True)

if __name__ == '__main__':
    main()