Prerecorded audio files must be:
- an 8KHz 8-bit mu-law .au file
- an 8KHz 8-bit mu-law .wav file
- an 8KHz 8-bit a-law .au file
- an 8KHz 8-bit a-law .wav file
- an 8KHz 16-bit linear .au file
- an 8KHz 16-bit linear .wav file
Note: 16-bit linear files will take twice as much storage and download
time. For better performance, use 8-bit files. However, if you use 8-bit files,
make sure they are compatible with the telephony environment you use. For
example, if you are in North America, use μ-law recordings. If you use
the wrong encoding, the audio file will need to be converted which may cause
a degradation in the audio quality.