Wolfram Language & System 10.0 (2014)|Legacy Documentation

This is documentation for an earlier version of the Wolfram Language.View current documentation (Version 11.2)

AU (.au)

  • Import and Export support all audio codecs commonly used in the AU format.


    Registered MIME type: audio/basic
    AU audio format.
    Used for digital audio in computer and telecommunication systems and on the web.
    Supports a variety of audio codecs, including lossless uncompressed PCM, μ-law, a-law, and ADPCM voice compression.
    Sometimes referred to as μ-law format or Unix Audio Format.
    The μ-law algorithm is a standard method for compressing the dynamic range of a signal.
    AU is an acronym derived from Audio.
    Binary file format.
    Supports various sampling frequencies and an arbitrary number of channels.
    Identical to the SND format.
    Developed by Sun Microsystems in 1992.

Import and ExportImport and Export

  • Import["file.au"] imports an AU file, returning a sound object.
  • Export["file.au",expr] exports a sound object to an AU file encoded using 8-bit pulse code modulation.
  • Import["file.au"] gives an expression of the form Sound[SampledSoundList[data,r]].
  • Export["file.au",expr] creates an AU file from the sound object expr.
  • Import["file.au",elem] imports the specified element from an AU file.
  • Import["file.au",{elem,suba,subb,}] imports a subelement.
  • Import["file.au",{{elem1,elem2,}}] imports multiple elements.
  • The import format can be specified with Import["file","AU"] or Import["file",{"AU",elem,}].
  • Export["file.au",expr,elem] creates an AU file by treating expr as specifying element elem.
  • Export["file.au",{expr1,expr2,},{{elem1,elem2,}}] treats each as specifying the corresponding .
  • Export["file.au",expr,opt1->val1,] exports expr with the specified option elements taken to have the specified values.
  • Export["file.au",{elem1->expr1,elem2->expr2,},"Rules"] uses rules to specify the elements to be exported.
  • See the reference pages for full general information on Import and Export.
  • ImportString and ExportString support the AU audio format.


  • General Import elements:
  • "Elements"list of elements and options available in this file
    "Rules"full list of rules for each element and option
    "Options"list of rules for options, properties and settings
  • Data representation elements:
  • "Data"raw audio samples, given as a list of lists of real numbers, each sublist representing an individual audio channel
    "SampledSoundList"AU file given as SampledSoundList
    "Sound"Sound object that plays as the sound
  • The element corresponds to the first argument of SampledSoundList.
  • Multiple channels are represented as an array of audio samples.
  • Import and Export use the element by default for AU files.
  • Advanced Import element:
  • "SampleRate"number of amplitude samples per second and channel


  • General option:
  • SampleRateAutomaticnumber of audio samples per second for each channel
  • Detailed properties and settings:
  • "AudioChannels"Automaticthe number of audio channels in the file
    "AudioEncoding""Integer8"how samples are encoded
  • If the sample rate is not specified when exporting to AU, the highest sample rate occurring in the exported sound is used, and all sounds are resampled as necessary.
  • If the number of channels is unspecified, the highest number of simultaneous channels is taken, and silence is inserted if necessary.
  • If is set to a value n which is less than the number of channels to be exported, only the first n channels are exported.
  • The AU format supports PCM (pulse code modulation) and ADPCM (adaptive differential pulse code modulation) codecs, and various other audio encoding algorithms.
  • can be set to any of the following codecs:
  • "Integer8"8-bit PCM
    "Integer16"16-bit PCM
    "Integer24"24-bit PCM
    "Integer32"32-bit PCM
    "Real32"32-bit IEEE floating point
    "Real64"64-bit IEEE floating point
    "aLaw"a-Law 4-bit PCM (ITU-T G.711)
    "uLaw"μ-Law 4-bit PCM (ITU-T G.711)
    "G721-32"32 kbps ADPCM (ITU G.721)
    "G723-24"G.723 encoding at 24 kbps
    "G723-40"G.723 encoding at 40 kbps
  • Not all codecs support arbitrary sample rates and channel specifications.

ExamplesExamplesopen allclose all

Basic Examples  (1)Basic Examples  (1)

Use Play to create a short sound sample, and export it to AU:

Click for copyable input
Click for copyable input
Introduced in 1999