Как извлечь из wav-файла два канала?

import wave
import math
import struct
fileName = "audio.wav"#file to be imported (change this)
#read file and get data
w = wave.open(fileName, 'r')
numframes = w.getnframes()
frame = w.readframes(numframes)#w.getnframes()
frameInt = map(ord, list(frame))#turn into array
#separate left and right channels and merge bytes
frameOneChannel = [0]*numframes#initialize list of one channel of wave
for i in range(numframes):
    frameOneChannel[i] = frameInt[4*i+1]*2**8+frameInt[4*i]#separate channels and store one channel in new list
    if frameOneChannel[i] > 2**15:
        frameOneChannel[i] = (frameOneChannel[i]-2**16)
    elif frameOneChannel[i] == 2**15:
        frameOneChannel[i] = 0
    else:
        frameOneChannel[i] = frameOneChannel[i]
#convert to string
audioStr = ''
for i in range(numframes):
    audioStr += str(frameOneChannel[i])
    audioStr += " "#separate elements with comma
fileName = fileName[:-3]#remove .wav extension
text_file = open(fileName+"txt", "w")
text_file.write("%s"%audioStr)
text_file.close()

frameOneChannel[i] = frameInt[4*i+1]*2**8+frameInt[4*i]
к виду: 
frameOneChannel[i] = frameInt[2*i+1]*2**8+frameInt[2*i]