Python synth noise generator

import scipy.io.wavfile
import numpy as np
import random

sr = 44100
duration = 10 # secs
y = np.zeros((sr*duration), dtype='float')

func_names = ('saw', 'square', 'tri', 'sin')
funcs = [
    lambda i, l: i/(l-1) * 2 - 1, # saw
    lambda i, l: round(i / (l-1)) * 2 - 1, # square
    lambda i, l: min(i/l,-(i/l-0.5))*4 if i/l < 0.5 else max(-(i/l-0.5), i/l-1)*4, # tri
    lambda i, l: np.sin(np.pi*2 * i/l) # sin
]

for func in range(len(func_names)):
    print('processing', func_names[func])
    try:
        index = 0
        while True:
            length = random.randint(10, 50)
            mul = random.uniform(0.2, 1)
            for i in range(length):
                y[index] = funcs[func](i, length) * mul
                if index % sr == 0:
                    print(index/sr, 'sec')
                index += 1
    except:
        pass

    scipy.io.wavfile.write(func_names[func] + '_noise.wav', sr, y)