Free online AU to WAV converter

Older Unix, Sun, NeXT, Java, and speech-recording software may produce AU files that modern editors, video applications, or hardware do not recognize. Converting one to WAV supplies a more widely supported PCM file for editing, playback, or transfer.

What the AU format is

AU, also called Sun Audio or NeXT/Sun audio, normally uses the .au or .snd extension. Its header records the encoding, sample rate, channel count, data offset, and data length.

An AU file may contain uncompressed PCM, 8-bit G.711 μ-law or A-law, or another encoding supported by the software that created it. AU files are most often encountered in older Unix utilities, Sun workstations, Java applications, legacy websites, telephone recordings, and older audio editors. The extension alone does not identify the audio codec.

What the WAV format is

WAV is a RIFF container commonly used for uncompressed PCM audio. It is recognized by most operating systems, digital audio workstations, video editors, media players, CD-authoring software, and audio hardware, although support for unusual WAV codecs can vary.

PCM WAV is suitable when an application requires standard audio, when you need to edit without adding another lossy-compression stage, or when you need a broadly compatible file. It is usually much larger than MP3 or other compressed formats because PCM stores each sample directly.

Convert with 101convert.com

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

This option requires no desktop installation. Check the downloaded file in the intended player or editor, particularly if the source uses an uncommon AU encoding.

Convert with FFmpeg

FFmpeg is useful for local or batch conversion. Inspect the source first:

ffprobe "input.au"

Convert it to 16-bit signed PCM WAV with:

ffmpeg -i "input.au" -c:a pcm_s16le "output.wav"

This keeps the source sample rate and channel count unless other options are supplied. Quotation marks preserve spaces in filenames. Other common PCM output choices are:

• -c:a pcm_s16le for 16-bit integer PCM
• -c:a pcm_s24le for 24-bit integer PCM
• -c:a pcm_s32le for 32-bit integer PCM
• -c:a pcm_f32le for 32-bit floating-point PCM

Change the sample rate or channel count only when the destination requires it; for example, -ar 44100 sets 44.1 kHz and -ac 2 sets two channels:

ffmpeg -i "input.au" -ar 44100 -ac 2 -c:a pcm_s16le "output.wav"

Convert with Audacity

1. Open Audacity and choose File → Import → Audio, then select the AU file.
2. Check the project sample rate and track channels. If Audacity asks to convert the file to the project rate, retain the source rate unless the destination needs another value.
3. Choose File → Export Audio, select WAV, and choose a PCM option such as 16-bit PCM.
4. Set the output filename, confirm the export, and inspect the exported file.

Quality and compatibility limits

Conversion does not restore information missing from the source. An 8-bit μ-law AU speech recording remains limited by its original bandwidth, quantization, and telephony encoding after it is decoded into 16-bit WAV. The larger bit depth provides a PCM representation but does not create new detail.

16-bit PCM WAV is generally the safest choice for ordinary playback, editing, and compatibility. Preserve the original sample rate and mono or stereo layout when possible. Changing mono to stereo duplicates the mono signal; it does not create stereo information. Resampling can also introduce small processing differences, so avoid it unless required.

If FFmpeg cannot decode the file or reports a missing AU header, the file may be truncated, mislabeled, or raw audio rather than a standard AU file. Raw audio has no reliable header and requires the correct encoding, sample rate, channel count, byte order, and sometimes sample format to be specified manually before conversion.