Free online WAV to AU converter

A legacy Sun, NeXT, Unix, Java, or telephony application may require an AU file instead of a RIFF/WAV file. Converting a PCM WAV to PCM AU normally preserves the audio while changing the container and byte order.

What the WAV format is

WAV is a RIFF container developed by Microsoft and IBM. It commonly stores uncompressed PCM audio and records the sample rate, channel count, bit depth, and other format data in its header.

Windows audio tools, Audacity, Adobe Audition, digital audio workstations, game-development tools, recording interfaces, and audio APIs create or accept WAV files. WAV is used for microphone recordings, edited exports, sound effects, and high-quality interchange. Although PCM is standard for editing and archiving, a WAV file can also contain compressed audio codecs.

What the AU format is

AU, also called Sun audio or NeXT audio, was introduced for Sun and NeXT systems. Its header specifies the data offset, encoding, sample rate, channel count, and data length. AU commonly stores big-endian PCM, but it also supports μ-law, A-law, and other older encodings.

AU remains useful with legacy Unix utilities, Java audio applications, telephony systems, and programs that specifically require a .au filename and Sun audio header. 16-bit big-endian PCM is a practical target when the receiving software supports it. PCM AU is not inherently smaller than PCM WAV; both contain approximately the same audio data, with differences mainly in header structure and byte order.

How to convert a WAV file to AU

Using 101convert.com

1. Open the WAV-to-AU converter on 101convert.com.
2. Upload the .wav file and select AU as the output format.
3. Start the conversion and download the resulting .au file.

This option requires no installed software. Check the downloaded filename and test the file in the application that requires AU. Do not upload confidential audio unless the service's handling of uploaded files is acceptable for your use.

Using FFmpeg

FFmpeg creates a broadly compatible AU containing 16-bit signed big-endian PCM:

ffmpeg -i input.wav -c:a pcm_s16be output.au

The command retains the input sample rate and channel count unless you specify different values. For stereo at 44.1 kHz, use:

ffmpeg -i input.wav -ar 44100 -ac 2 -c:a pcm_s16be output.au

For a telephony system requiring 8 kHz mono μ-law, use:

ffmpeg -i input.wav -ar 8000 -ac 1 -c:a pcm_mulaw output.au

μ-law is lossy and narrow-band, so use it only when the destination requires that encoding.

Using Audacity

Open the WAV file in Audacity and choose File → Export Audio. Select AU (Sun/NeXT) or the equivalent AU/Sun export type, choose the destination, and export. Set the sample rate, channel layout, and encoding to the values required by the destination. If AU is unavailable in that Audacity build, use FFmpeg or 101convert.com.

Quality and compatibility limits

Converting PCM WAV to PCM AU does not add lossy compression, but exporting a 24-bit or 32-bit source as pcm_s16be reduces its bit depth. Keep the original WAV as the archive master.

Changing the sample rate or channel count changes the audio and may be necessary for older AU readers. Mono-only software requires downmixing, and some applications accept only specific combinations such as 8-bit μ-law, 16-bit PCM, 8 kHz, or 44.1 kHz.

AU support varies between modern applications. Readers may reject uncommon encodings, metadata, or very large files. Inspect the result with ffprobe output.au if playback fails, then try 16-bit big-endian PCM with the required sample rate and mono or stereo layout.