How to Get IVR and Phone Audio Right
Recording and formatting prompts for phone systems, such as menus and hold messages, which play through narrow-bandwidth telephone audio.
Tomas Lindqvist
The key figures
- Common format
- 8 kHz, 8-bit mu-law WAV for many US phone systems
- Bandwidth
- traditional telephone audio covers roughly 300 Hz to 3.4 kHz
- G.711
- the ITU standard for telephone audio encoding
- Clarity
- slower, clearly articulated speech works best
Why this is worth getting right
Phone lines strip much of the audio spectrum, so prompts that sound fine in the studio can become hard to understand on a call.
Do this, not that
Do
- Deliver in the format your phone system specifies
- Record at high quality and convert at the end
- Test prompts on real phone calls
- Keep menus short with the most common options first
- Match voices and levels across prompts
Don’t
- Music-heavy prompts that distort on phone lines
- Long menus with many options
- Mismatched voices between prompts
- Uploading files in the wrong format
When to bring in help
Our advice Bring in help when setting up or refreshing phone system prompts.
Where this comes from
- International Telecommunication Union — G.711 Pulse code modulation of voice frequencies
- Microsoft Learn — Audio file formats for Teams auto attendants
The figures and practices above come from the sources listed.
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Where to go next
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