The supported sound formats (and their proper file extensions) for the Tropo platform are as follows:
8kHz, 8bit u-law (wav or raw) (*.wav or *.ulaw)
8kHz, 8bit a-law (wav or raw) (*.wav or *.alaw)
8kHz, 8bit pcm (wav) (*.wav)
8khz, 16bit pcm (wav or raw) (*.wav or *.pcm)
MS-GSM (wav) (*.wav)
GSM 6.10 (raw) (*.gsm)
You can use other formats like MP3, but they will be automatically downsampled and converted due to limitations in telephony standards, so it's always best to have your files in 8bit, 8Khz u-law format from the start.
