Audio Specifications: Formats: MP3, WAV, WMA, or OGG.
Bitrate: At least 128 kbps; MP3 files must be fixed bitrate (CBR), not variable bitrate (VBR).
No silences at the beginning or end of the recordig/file.
Duration: 15 to 60 seconds (15 and 30 seconds are the most common).
Tracking Pixels
Format: 1x1 pixel only.
Supported Events: Audio printout and quartiles.