In my tests, if I record a call in .wav format, a 10 second file is about 177,000 bytes, while a 10 second .gsm file is 17,000 bytes. I then used sox to convert the .gsm file to a .wav file, and it stayed at around 17,000 bytes. So, is the default recording format for .wav using a higher sample rate? vs the default conversion format for the sox tool? checking the file type using "file" I see that the larger one is: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz and the wav created by sox via the default conversion from .gsm is: RIFF (little-endian) data, WAVE audio, GSM 6.10, mono 8000 Hz So apparently the larger wav file is 16 bit... how are these recording parameters controlled? Can I set it to record directly into the smaller wav format? Or will I have to run sox on every file...