Introduction to audio files in the telephony environment
Aircall operates on a fixed telephony standard: 8-bit PCM mono uLaw with a sampling rate of 8 kHz.
Because this telephony format is fixed, any audio file uploaded to Aircall is automatically transcoded to this standard.
This standard is bandwidth-limited to the 300 Hz to 8 kHz audio range. It is designed for voice transmission and provides acceptable voice-quality results. It is not suitable for high-quality music reproduction, but it delivers minimally acceptable results for telephony use.
Audio file requirements and recommendations
To ensure your audio files play correctly on your Aircall phone numbers, they must meet the following requirements.
| Requirement | Specification | Additional notes |
|---|---|---|
| File type | MP3 only | Renaming a file extension to .mp3 does not convert it to MP3 format. The file must be properly converted using an audio conversion tool. |
| File name | No special characters | Special characters such as #, $, ^, and similar symbols are not allowed. If present, Aircall automatically replaces them with spaces. |
| File size | Under 9.57 MB | Files larger than this limit cannot be uploaded. |
| Bitrate | 16 kbps or lower | Higher bitrates are not recommended and may cause issues. |
| Audio frequency | 16 kHz or lower | Sampling frequencies above this value are not recommended. |
| Audio channels | Mono | Stereo files are automatically converted to mono, as mono is the telephony standard. |
How to convert your audio file
You can convert your audio file using online or desktop tools such as Vocaroo, Audacity, or Online Convert.
When converting the file, make sure to select the values described in this article, including MP3 format, mono channel, appropriate bitrate, and sampling frequency.
Apple software compatibility notice
Important: Apple software adds specific audio recording metadata that is not compatible with Aircall.
If you record audio using macOS or iOS, you must convert or compress the file before uploading it to Aircall. This ensures the audio metadata is compatible with the platform.
Impact of an invalid audio file
If an uploaded audio file does not meet the required specifications, inbound calls to the phone number may be affected.
Callers may experience dead air, an error message, or a call disconnection with the message:
"An error occurred during the call."
To resolve this issue, convert the original audio file according to the requirements listed above and upload the converted version to Aircall.
For instructions on uploading audio files, please see our article Smartflows: Configure call messages and music (Audio, Waiting music, Voicemail, IVR).
Tip: You can also use the Record audio option in the Type of message drop-down menu to record your message directly from the Aircall Dashboard. This is the fastest way to avoid any format or compatibility issues.
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