Introduction to audio files in the telephony environment

The telephony standard is 8-bit PCM mono uLaw with a sampling rate of 8Khz.

Since this telephony format is fixed, any audio file uploaded will be transcoded to that telephony standard.

That standard is bandwidth-limited to the 300 Hz – 8 KHz audio range and is designed for voice and provides acceptable voice-quality results. This standard isn’t suitable for quality music reproduction, but will provide minimally acceptable results.

Audio file requirements and recommendations

  • File Type

Aircall supports only MP3 files. Note that changing the extension of your file to <filename>.mp3 does not change it to MP3. To properly convert it to MP3 format, please use the recommendations below for file conversion.

  • File Size

Your file should be under 10 MB.

  • Bitrate

Your file should be recorded at 16 kbps or lower bitrate.

  • Audio Frequency

Your file should be recorded at 8 KHz or lower frequency.

  • Audio Channels

Your file should be recorded at Mono instead of Stereo. Note that it would be later converted to mono, as mono is the telephony standard.

How to convert your file to these parameters?

You can convert your file using an online recording service such as Vocaroo, Audacity, or Online Convert. Just ensure that you select the corresponding values, as per the documentation above, and as seen at the image below.

Alert of Apple’s softwares:

Note that Apple's software adds specific audio recording data that is not compatible with Aircall and will need to be converted. Please make sure that if you record the message via macOS or iOS, send it through a converter or compressor to ensure the metadata is compatible.

What is the impact of an invalid audio file:

In case the audio file does not meet the requirements, this will impact the inbound calls to your phone line. People calling the phone line will experience dead air, an error or disconnect message: "An error occurred during the call."

To solve this issue, please convert your original audio file according to the recommendations above, and upload the converted file to Aircall. After the file conversion, to know more about how to upload a file you can follow Configuring Numbers: Voicemail, Music, and Messages.


Still in need of assistance? Please feel free to reach out to the Support Team and we will be happy to assist!

Did this answer your question?