bif.py

rate = 44100
total_time = 60
iterations = 2**6
f0 = 440 * pow(2, -4 + 1)
f1 = 440 * pow(2, -4 + 8)
a0, a1 = 2.4, 4.0
import numpy as np
rs = np.linspace(a0, a1, rate * total_time, dtype=np.float64)
wav = np.zeros(len(rs), dtype=np.float64)
xs = np.full(len(rs), 0.5, dtype=np.float64)


def lerp(a, b, t):
    return a * (1 - t) + b * t


for i in range(iterations):
    print(f'{i/(iterations-1):%} complete')
    xs = rs * xs * (1 - xs)
    xm = pow(2, lerp(np.log(f0) / np.log(2), np.log(f1) / np.log(2), xs))
    wav += np.cos(2 * np.pi * np.cumsum(xm) / rate)
wav /= np.max(np.abs(wav))
import scipy.io.wavfile
scipy.io.wavfile.write('bif.wav', rate, wav)