create a raw file with silence. for example 1 second, 16 bit mono at 44100 Hz: dd if=/dev/zero of=silence.raw bs=44100 count=2 and convert it to wav: sox -t raw -r 44100 -s -w -c 1 silence.wav
sorry, that should be sox -t raw -r 44100 -s -w -c 1 silence.raw silence.wav
