Audio sampling rates and formats.

Ever wondered how many sampling rates, audio formats and compression methods there are in this world? Here's a list with a short explanation.

Sampling Rates
Audio Formats

The info is here and there enriched with data from the AudioFormats-files by Guido van Rossum, with his personal approval.
Thank you Guido.

Sampling Rates.




One fourth of the Mac sampling rate (rarely seen).


One third of the Mac sampling rate (rarely seen).


Exactly 8000 samples/sec is a telephony standard that goes together with U-LAW (and also A-LAW) encoding. Some systems use an slightly different rate; in particular, the NeXT workstation uses 8012.8210513, apparently the rate used by Telco CODECs.

11 k

Either 11025, a quarter of the CD sampling rate, or half the oldfers Macs sampling rate (used to be perhaps the most popular rate on the Mac until 44 Khz sampling became available with 640AV and 840AV Quadra's and later the PowerPC Macintoshes).


Used by, e.g. the G.722 compression standard.

18.9 k

CD-ROM/XA standard.

22 k

Either 22050, half the CD sampling rate, or the Mac rate; the latter is precisely 22254.545454545454 but usually misquoted as 22000. (Historical note: 22254.5454... was the horizontal scan rate of the original 128k Mac).


Used in digital radio, NICAM (Nearly Instantaneous Compandable Audio Matrix [IBA/BREMA/BBC]) and other TV work, at least in the UK; also long play DAT and Japanese HDTV.

37.8 k

CD-ROM/XA standard for higher quality.


This weird rate is used by professional audio equipment to fit an integral number of samples in a video frame.


The CD sampling rate. (DAT players recording digitally from CD also use this rate.). Unlike the older Macs of a few years ago, allmost all PowerPC Macs (including the new G3's) support audio sampling at 44.1 Khz.


The DAT (Digital Audio Tape) sampling rate for domestic use.


When producing digital audio on your Mac, only use the following sample rates. They are widly supported and accepted:

  • 8000 8-bit U-LAW mono,
  • 22050 8-bit linear unsigned mono and stereo,
  • 44100 16-bit linear signed mono and stereo.

Audio Formats.


669 tracker module


Audio Interchange File Format Developed by Apple (who else...;-) for storing high-quality sampled sound and musical instrument data.
AIFF and AIFF-C: (.aif, .aiff, .aifc) AIFF stands for Audio Interchange File Format and was developed by Apple for storage of sounds in the data fork. It has been adopted by SGI and some other specialized applications. The Macintosh OS includes support for playing and creating AIFF files. More information about the format can be found in Inside Macintosh VI or Inside Macintosh: Sound. In addition, the format specification can be found at various places on the Internet. AIFF is a very flexible file format, allowing the specification of arbitrary sampling rates, sample size, number of channels, and application-specific format chunks which can be ignored by other applications. AIFF-C is basically AIFF with compressed samples. Apple supports two proprietary types of compression on the Macintosh, MACE 3-to-1 and MACE 6-to-1. Both are lossy compression algorithms, but provide reasonable quality with a great space savings. Recently, Apple has added support for µ-law and IMA 4:1 sub-formats, which are described below. In addition, the Apple II GS uses ACE 2-to-1 and ACE 8-to-3 compression. The very wellknown audioplayer SoundApp does not supports ACE files. Unlike SoundCap/Edit, 8-bit samples are stored as two's complement values. Lossy compression means the compressed sound will not sound exactly like the original sound, much like JPEGs do not look exactly like the original picture.


Velvet Studio Instruments


European telephony format audio. See also: AU


Extreme's Tracker module format


Velvet Studio Module


Velvet Studio Sample


Sun/NeXT/DEC Audio file.
Sun Audio and NeXT: (.au, .snd) Internally, these are the same formats. SoundApp differentiates between them by file type or suffix merely for the user's benefit. The format specifies arbitrary sampling rates and multi-channel sounds. It supports a number of sound encodings, including µ-law, a-law, various linear formats of varying sample sizes, floating point samples, native DSP samples and G.72x ADPCM compression. SoundApp supports µ-law, a-law, 8-bit signed, 16-bit signed, G.721 ADPCM and both versions of G.723 ADPCM. Each µ-law sample is stored in 8 bits, but the meaning of the sample is different. Normal sound formats use linear encoding, whereas µ-law and a-law are logarithmic. This means that the spacing between the different sound levels grows progressively larger as the values increase. This format provides a larger dynamic range than normal 8-bit samples, approximately equivalent to 12-bit samples. However, it suffers from more noise than linear encodings. The G.721, G.723-24 and G.723-40 ADPCM formats are CCITT standards for compression of 8000-Hz 14-bit samples into a 32-, 24- or 40-kbps data stream. These compressed formats are not very popular due to the extremely slow decompression rates. Most files start with the four-character signature, '.snd', but there are some older, headerless .au files. These are assumed to be µ-law encoded, mono at 8000 Hz. A ".al" suffix will force the sound to be a-law, if it does not have a header. The U.S. telephone system uses µ-law encoding for digitization, whereas the European telephone systems use a-law encoding.


MS Audio Video Interleave file


Audio Visual Research sound file, used by some high-end commercial audio software. It can include some midi information.


Typhoon wave files


Raw Audio-CD data.
Raw Audio CD Data: Raw 44.1-kHz, stereo, 16-bit samples in little endian format used by some CD-ROM authoring programs. SoundApp can play this format.

CD Audio

Audio CD Tracks: Using QuickTime SoundApp can extract the digitial data from audio CDs via the Import To QuickTime option. It will bring up a dialog box which allows various parameters to be set for the conversion. Be aware that audio tracks take up a huge amount of disk space.


DCM module format


Macintosh SoundCap/SoundEdit recorded instrument format.
SoundCap: This is a Macintosh sound format created for use with an early audio digitizer. Version 4.3 of the application circa 1986 is the latest. It was written by Mark Zimmer and Tom Hedges from Fractal Software. It supported two basic flavors of sounds, compressed and uncompressed. Both types had 'FSSD' as the file type and 'FSSC' as the creator. Uncompressed files are just a series of 8-bit unsigned bytes in the data fork. Compressed files store information pertaining to sampling rate and a checksum. Sampling rates are limited to 5.6, 7.4, 11.1 and 22.2 kHz, and compression is done with a Huffman algorithm. Compressed SoundCaps are sometimes referred to as HCOM files because that is the first four characters of the file. SoundCap files can be played with SoundApp.


Digilink format


Sound Designer I audio file


DownLoadable Sounds


Delusion/XTracker Digital Music Fileformat


Delusion/XTracker Digital Sample Fileformat


Digital Sound Module tracker format


DigiTrekker module


DVI ADPCM: (.adpcm) This is the Intel/DVI ADPCM (Adaptive Differential Pulse Code Modulation) format. It is a 4-to-1 compressed 16-bit file format. It is unique among the various ADPCM formats in that it's very fast, and like all ADPCM formats it is lossy. SoundApp supports the version of the format that plays mono at a 8000-Hz sampling rate.


DiamondWare Digitized file


Ensoniq ASR disk image


Ensoniq EPS disk image


Ensoniq KT disk image


Ensoniq SQ1/SQ2/KS32 disk image


Ensoniq SQ80 disk image


Ensoniq VFX-SD disk image


Ensoniq ASR file


Ensoniq EPS file


Ensoniq KT file


Ensoniq SQ1/SQ2/KS32 file


Ensoniq SQ80 file


Ensoniq VFX-SD file


ABT Extended MoDule


ESPS audio files


Ensoniq EPS family compacted disk image


Farandoyle linear module format


Farandoyle blocked linear module format


Farandoyle tracker module


GUS PnP bank file format


FunkTracker module format


Farandoyle Sample format


Raw CCITT G721 4bit ADPCM format data


Raw CCITT G723 3 or 5bit ADPCM format data


Ensoniq EPS family disk image file


Raw GSM 6.10 audio stream.
GSM: (.gsm, .au.gsm) This compression algorithm is the European GSM 06.10 standard for full-rate speech transcoding, prI-ETS 300 036, which uses RPE/LTP (residual pulse excitation/long term prediction) coding at 13 kbit/s. It was developed for the European digital cellular phone system to make the most of tight bandwidth. Basically, what this means is that it analyzes and derives a mathematical formulation of small sections of speech using a model of the human vocal tract. Thus, it is optimized for speech reproduction and is in fact used in may Internet phone applications, although it seems to compress arbitrary sounds relatively well. The ".au.gsm" format consists of a series of 33-byte frames at sampled at a mono 8000 Hz. In spite of the fact that the suffix contains ".au" the files are not related to the Sun Audio (AU) files. The WAVE implementation uses a slight variation on the algorithm (they're good with these standards!) and can support mono files at an arbitrary sampling rate. SoundApp supports this file format.


US Robotics voice modems / QuickLink GSM format


Sound Tools HCOM format


Interchange file format
Amiga IFF (8SVX): (.iff) This is the dominant format on the Commodore Amiga platform. It can specify an arbitrary sampling rate but only supports 8-bit sounds in stereo or mono. It also supports a 2-to-1 lossy compression format which uses a unique Fibonacci-delta compression algorithm. This format is supported by SoundApp.


IMA ADPCM: This is a cross-platform standard from the Interactive Multimedia Association for sound playback. The basic algorithm is the same as in DVI ADPCM. SoundApp currently supports IMA data in WAVE, AIFF-C and 'snd ' resources. Unfortunately, Apple and Microsoft store their data in different ways. (So much for standards!) Both mono and stereo sounds are supported at an arbitrary sampling rate; however, the compression algorithm only accepts 16-bit samples.


MWave DSP synthís mwsynthini GM-setup


Gravis UltraSound bank setup


INRS-Telecommunications audio


Ensoniq EPS family instrument


Sample Cell / II Mac instrument


Sample Cell / II PC instrument


IRCAM: (.sf) These files are used by academic music software such as the CSound package and the MixView sound sample editor. These files also specify an arbitrary sampling rate and can contain mono or stereo files. SoundApp only supports 8- and 16-bit samples, although the format can contain other encodings, e.g. floating point. The IRCAM format is supported by SoundApp.


Digitrakker Instrument File


Impulse Tracker module/instrument/sample


Kurzweil 2500 sample


Kurzweil 2000 sample (multi-floppy)


Kurzweil 2000 sample


Matlab variables binary file


MAUD sample format


Digitrakker Module


OctaMED tracker module


MIDI: (.mid, .midi, .kar) Musical Instrument Digitial Interface is primarily a standard for communication between musical instruments. General MIDI (GM) is a standard for storing compositions based on what events happened during the performance. It does not contain digitized audio data; instead, it stores only the information about which notes were played in a time-line format. This is similar to the MOD format but without the digitized instrument samples. QuickTime 2.0 and later supports General MIDI data in QuickTime movies. SoundApp can directly play type 0, 1 and 2 MIDI files using QuickTime or OMS 2.1 or later and can also play MIDI data embedded in QuickTime movies. Note that lyric information from karaoke files is not displayed. There are several extensions to the GM standard, including GS (Roland) and XG (Yahama). SoundApp supports both of these extensions. It will also send all System Exclusive data to the selected MIDI output device if you are using the OMS MDI driver.


MOD: (.mod, .s3m, .mtm) This is not really a sound format but a music format. The format was "born" on the Amiga platform. It stores (1) digitized instruments and contains (2) a musical score (sequencing information that determines how and when to play which samples) which produces a lengthy composition with a very small amount of data.
The sequencing information in a MOD file contains 4 tracks of information describing which, when, for how long, and at what frequency samples should be played. This means that a MOD file can have up to 31 distinct (digitized) instrument sounds, with up to 4 playing simultaneously at any given point. This allows a wide variety of orchestrational possibilities, including use of voice samples or creation of one's own instruments (with appropriate sampling hardware/software). The ability to use one's own samples as instruments is a flexibility that other music files/formats do not share, and is one of the reasons MOD files are so popular, numerous, and diverse.
There have been various extensions to this format, but SoundApp only supports a subset using two different drivers. These include Amiga SoundTracker, NoiseTracker, Protracker, Amiga StarTracker (4- and 8-track), Oktalyzer (4-8 tracks), Amiga MED/OctaMED (4-16 tracks, MMD0/1/2 formats), IBM FastTracker (4-, 6- and 8-track), IBM TakeTracker (1-32 tracks). Using the ZSS driver, SoundApp also supports S3M (ScreamTracker 3), MTM (Multitracker) and the 'MADF' and 'MADG' formats used by Player Pro for the Macintosh. Playback of XM or 669 files is not currently supported by either driver.


QuickTime Movies: (.mov) This is the Apple standard for time-based multimedia files. Versions 1.x support moving pictures, sound and later versions support text. QuickTime 2.0 added MIDI tracks via a software synthesizer or external synthesizer in 2.5 and later. QuickTime 2.0 or later and the QuickTime Musical Instruments extension must be installed in order to play QuickTime MIDI files with SoundApp. SoundApp can deal with MACE, IMA and µ-law compressed QuickTime sound tracks.


MPEG Audio: (.mp, .mp2, .mp3, .m1a, .m2a, .mpg, .mpeg, .swa) MPEG stands for the "Moving Picture Experts Group," working under the joint direction of the International Organization for Standardization (ISO) and the International Electro-Technical Commission (IEC). This group works on standards for the coding of moving pictures and associated audio. MPEG audio files can be either layer I, II or III. Increasing layer numbers add complexity to the format and require more effort to encode and decode. However, they also provide higher playback quality for the sample bit rate. SoundApp supports layers I, II and III. To further complicate matters, MPEG files come in two flavors, MPEG-1 and MPEG-2. The encodings for the three layers are mostly the same; however, MPEG-2 streams have more compact header information. Files can have sampling rates of 32000, 44100 and 48000 Hz for MPEG-1 and 16000, 22050 and 24000 Hz for MPEG-2. Data can be in stereo or mono and decompresses to 16-bit resolution. MPEG compression is a lossy algorithm based on perceptual encodings, which can achieve high rates of compression without noticable decreases in quality. Typical compression rates are around 10-to-1. SoundApp supports MPEG audio only on Macs with a PowerPC processor. Finally, Macromedia's Shockwave streaming audio system uses a MPEG-1 Layer III encoding with a non-standard header, which SoundApp will ignore. They frequently have a ".swa" suffix.
More info on MPEG Audio can be found at


MultiTracker Module


Mus10 audio


MWave DSP synthís instrument extract


NIST Sphere audio


Typhoon vOice file


Oktalyzer tracker module


SB Studio II package


Advanced Gravis Ultrasound / Forte tech Patch


OKI MSM6376 synth chip PCM format


DisorderTracker2 module


DisorderTracker2 sample


WAVmaker program


Pinnacle Sound Bank


PSION a-law audio.
PSION sound: (.wve) This format consists of a short header followed by a-law encoded samples at 8000 Hz. It is used by the PSION Series 3 palmtop personal information manager and uses a ".WVE" suffix.


Protracker Studio Module Format


Poly Tracker module


RealAudio, streaming audio on Internet:


Raw signed PCM data


A format by Microsoft and IBM, first included within Windows 3.1. Better known as .WAV (see below).


RealMedia, streaming audio and video on Internet:


Signed 8bit Sample data


Raw Signed Byte (8bit) data


Emu SoundFont v1x Bank files / Creative Labs SB AWE 32


Sound Designer audio.
Sound Designer: Digidesign's predecessor to the Sound Designer II format. Unlike the second generation format, it does not use resources to store header information. It has a large header, although most of it is used internally by their software. It can only contain mono data. Most files are usually 16-bit, 44.1 kHz. SoundApp plays this fileformat. SD is also the standard working format for most professional harddisk recording software, such as Deck II.


Sound Designer II: This is a popular format for professional sound editing on the Macintosh. Deck II is a good example. It can specify arbitrary sampling rates and supports multiple channels and data sizes. Information regarding the specifics of the sound are stored in three 'STR ' resources. Like VOC, 8SVX and WAVE, samples are encoded as signed values. SoundApp plays this format.


Roland S-series floppy disk image


Raw Midi Sample Dump Standard file


Raw Signed DWord (32bit) data


Midi Sample Dump Standard files as compacted by SDX


IRCAM SoundFile format


Emu SoundFont v20 file


SoundStage Sound File Data


SoundStage Sound File Info


Sonic Foundry Sample Resource


Samplevision format


Ad Lib Gold Sample


See: AU


AKAI MPC3000 sample


Apple SND systemsound format
System 7 and 'snd ': System 7 sound files are simply type 1 'snd ' resources stored with a type of 'sfil' and a creator of 'movr'. System 7 provides the familiar icon for them and permits playback in the Finder by double-clicking on them. An 'snd ' is a type of resource which consists of a series of commands for use by the Sound Manager. In addition to digitized sound samples, 'snd ' resources can contain direct frequency-modulated and wave table-based sounds. Any number of the three types can be combined with various effects to produce complex sound files. Simple Beep is an example of a non-digitized 'snd '. There are two types of 'snd ' resources, amazingly called type 1 and type 2. Type 1 is the format described above and is referred to as the System sound format. Type 2 is for use with HyperCard and can contain only a sampled (digitized) sound. SoundApp can play both types but will only convert sampled sounds. For more information on 'snd ' files consult Inside Macintosh VI or Inside Macintosh: Sound. A familiarity with the Resource Manager would also be helpful. 8-bit samples are stored as unsigned bytes, like SoundCap/Edit, but 16-bit samples are signed, like AIFF. Stereo 'snd ' resources are also possible, but Sound Manager 3.0 or later is required to play 16-bit samples directly. The possible types of compression for 'snd ' resources are the same MACE, IMA and µ-law types used in AIFF-C files. SoundApp plays these files.


Sounder sound file


Sndtool sound file


SB Studio II sound




SoundEdit: This is the same file type as uncompressed SoundCap (DWEF) for mono sounds. In addition, it adds to the resource fork some information about colors, labels, looping segments and the format. The most useful for playback is the 'INFO' resource, which stores the sampling rate, limited to the same four as SoundCap. Stereo files consist of the left and right channels stored back-to-back in the data fork. MACE-3 and MACE-6 compression is supported for mono 22 kHz files only, which is a limitation of the SoundEdit. SoundEdit also supports 4:1 and 8:1 compression, but SoundApp does not support these proprietary compression algorithms. The 'INFO' resource specifies the lengths of each channel, which can be different. SoundEdit came with the MacRecorder sound digitizer from Farallon and later by Macromedia. SoundEdit Pro and SoundEdit 16 are more recent incarnations, and they support a much larger format suite, including up to 48-kHz samples and 16-bit resolution. They shed the limitations inherent in the original format. SoundApp does not currently support SoundEdit Pro or SoundEdit 16 files.


Speach Data file


Digitrakker Sample


SPPack sound sample


Studio Session Instrument: This format is primarily used with Super Studio Session and stores digitally sampled instruments. There are two types: compressed and uncompressed. Compressed instruments have the same format as compressed SoundCap files, and uncompressed instruments are likewise similar to uncompressed SoundCap files, with the addition of an eight-byte header.


Scream tracker v2 module


Scream tracker v3 instrument


Scream tracker v3 module


Interchange file format, 8SVX/16SV


Raw Signed Word (16bit) data


Shockwave audio: streaming audio on Internet:


Yamaha SY-series wave files (really named W??)


Ascii Text formatted audio data


Ascii Text parameter description


Yamaha TX16W wave files (really named W??)


Raw Unsigned Byte (8bit) data


Raw Unsigned DWord (32bit) data


US telephony format (CCITT G711) audio. See also: AU.


UltraTracker modules


MikMod 'UniMod' format


Raw Unsigned Word (16bit) data


UltraTracker Wave File


Covox 8bit audio


Annotated speech


Sound Blaster VOC: (.voc) This is the format used by the Creative Voice SoundBlaster hardware used in IBM-compatible computers and is optimized for that hardware. It specifies the sampling rate as a multiple of an internal clock and is not as flexible as the other general formats. Data can be segmented and portions of silence can be added. SoundApp supports both of these features, but not the looping feature.


Dialogic adpcm


Talking Technology Incorporated file


Yamaha waveforms (see TXW, SYW)


Yamaha TX16W wave


Yamaha SY-series wave


Windows WAVE: (.wav) This format was created by Microsoft and IBM, and it has unfortunately become a popular standard. Like AU, it specifies an arbitrary sampling rate, number of channels and sample size. It also specifies a number of application-specific blocks within the file. It has a plethora of different compression formats, although the Microsoft ADPCM is the most popular. SoundApp only supports 8-bit, 16-bit, 32-bit, µ-law, a-law, GSM-, IMA ADPCM- and MS ADPCM-compressed sounds. IMA and MS ADPCM provide a 4-to-1 compression ratio and GSM provides an approximately 9.7-to-1 compression ratio. All data fields and 16-bit samples are stored in little-endian notation, as Intel processors require. All other formats supported by SoundApp use big-endian notation which means the high-bytes come first in the data stream.


Turtle Beach WaveFront Bank (Maui/Rio/Monterey)


Turtle Beach WaveFront Drum set (Maui/Rio/Monterey)


Turtle Beach WaveFront Program (Maui/Rio/Monterey)


Psion sound


Fast Tracker 2 extended module


Fast Tracker 2 instrument

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