Free online VOX to AU converter

Source format: VOX

VOX is a simple audio file format most commonly associated with Dialogic ADPCM compressed speech recordings. It is often used in older telephony, voice logging, IVR systems, and some legacy dictation or voice-processing workflows. VOX files usually contain mono, low-sample-rate audio optimized for speech rather than music, so they are compact but limited in fidelity.

Target format: AU

AU is an older audio container format originally used on Unix systems and early Sun workstations. It can store several audio encodings, including PCM and some compressed variants, and is still recognized by many audio tools and development environments. AU is useful when you need a simple, widely understood legacy audio format for compatibility with Unix-based software or older systems.

How to perform the conversion

The most reliable way to convert VOX to AU is with FFmpeg, a free command-line tool that supports both formats.

1. Install FFmpeg if it is not already available on your computer.
2. Open a terminal or command prompt.
3. Run a command such as ffmpeg -f vox -i input.vox output.au.
4. If FFmpeg does not detect the VOX variant correctly, try specifying the audio parameters explicitly, for example ffmpeg -f s16le -ar 8000 -ac 1 -i input.vox output.au for raw telephony-style VOX audio.
5. Open the resulting output.au file in an audio player or editor to confirm that it plays correctly.

If you prefer a graphical workflow, you can also use desktop audio editors that support both formats, such as Audacity with FFmpeg support or other professional audio tools. Import the VOX file, then use File → Export or File → Export Audio and choose AU as the output format if available.

You can also convert the file on 101convert.com for free, without installing any software.

Notes on quality and compatibility

VOX files are usually speech-oriented and low fidelity, so converting them to AU does not improve audio quality; it only changes the container or encoding used for storage. If the source VOX is raw ADPCM or telephony audio, the output AU file may still sound narrow-band and mono.

Compatibility depends on the exact VOX variant. Some VOX files are treated as raw audio rather than a fully self-describing format, so conversion tools may need the correct sample rate and channel count to interpret them properly. The most common settings are 8 kHz and mono, but legacy files can vary.

AU is broadly compatible with older Unix tools, but modern players may have limited support compared with WAV or MP3. If you need maximum interoperability, consider converting to a more common format after verifying the AU output.