Better telephone system technology allows message on hold audio to be loaded directly into the phone system, rather than played from an outside source, such as a music on hold player.
If you’re using your phone system’s internal music on hold capabilities, you will need to know the required file format. You message on hold provider should be able to offer the correct format for your phone system.
Here is a list of the most commonly used file formats for telephone system music on hold:
PCM (pulse code modulation) refers to an uncompressed .wav file:
- PCM .wav 44.1 kHz, 16 Bit
- PCM .wav 48 kHz, 16 Bit
- PCM .wav 16 kHz, 8 Bit
- PCM .wav 8 kHz, 8 Bit
U-Law (also known as mu-law) and A-Law are special compression schemes:
- CCIT u-Law (.wav) 8 kHz, 8 Bit
- CCIT a-Law(.wav) 8 kHz, 8 Bit
ADPCM (adaptive pulse code modulation) differs from PCM, in that the PCM .wav files are stored using linear samples, while ADPCM uses deltas between samples.
- IMA ADPCM(.wav) 8 kHz, 4 Bit
Dialogic ADPCM files are always 4 Bit files. Learn more.
- DIALOGIC ADPCM (.vox) 6 kHz
- DIALOGIC ADPCM (.vox) 8 kHz
G711 is a type of U-Law or A-Law. More here.
- G711 u-Law (.vox) 6 kHz
- G711 u-Law (.vox) 8 kHz
- G711 a-Law (.vox) 6 kHz
- G711 a-Law (.vox) 8 kHz
MP3 is extremely common. Excellent results are obtained with a monaural 128 Kbps .mp3 file.
- MPEG-3 (.mp3) 128 Kbps
The .au file extension was begun by Sun Microsystems. It is similar to .wav formats, but requires the .aw file extension.
- .au u-Law 8 kHz, 8 Bit
- .au a-Law 8 kHz, 8 Bit
- .au PCM 8 Bit
- .au PCM 16 Bit
If converting your own files…
If you are converting audio from one file format to another, be aware that it is best to begin with the native file format, that is, the highest-quality original format in which the audio was created. Often this is a 16 Bit .wav file. To work with converting audio files, you might want to try the SwitchSound audio file converter.
