AU to NIST Converter

High-quality AU to NIST conversion online

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Server-Side Processing

All AU to NIST encoding runs in the cloud. Your computer or phone handles nothing — just upload and wait.

Universal Access

Whether you are on a PC, Mac, Chromebook, or smartphone, the AU to NIST converter works directly in your browser.

Faithful Conversion

Audio integrity is preserved when moving from AU to NIST. The converter handles sample rates and bit depths with care.

How to convert AU to NIST

1

Select files from Computer, Google Drive, Dropbox, URL or by dragging it on the page.

2

Choose nist or any other format you need as a result (more than 200 formats supported)

3

Let the file convert and you can download your nist file right afterwards

About formats

AU is an audio file format introduced by Sun Microsystems for its Unix workstations and the NeXT platform. It features a minimal 24-byte header specifying data offset, size, encoding type, sample rate, and channel count, followed by the audio payload. AU supports numerous encodings, including uncompressed linear PCM at various bit depths, mu-law and A-law companding (logarithmic compression used in telephone systems), and several ADPCM variants. This versatility made AU a workhorse across early Unix environments, web audio (Java applets defaulted to AU), and telephony applications. One advantage is simplicity: the compact header and straightforward structure make it trivial to parse, generate, and stream programmatically. The built-in mu-law option provides another benefit, delivering reasonable voice quality at just 8 KB per second — half the rate of 16-bit uncompressed audio — invaluable when storage and bandwidth were scarce. Although modern formats have largely supplanted AU in consumer applications, it retains a foothold in scientific computing and audio processing pipelines where minimal overhead and reliable cross-platform behavior are valued.
Developer: Sun Microsystems
Initial release: 1992
NIST SPHERE (SPeech HEader REsources) is a specialized audio file format created by the National Institute of Standards and Technology for speech research, particularly projects funded by DARPA. The format wraps raw audio samples with a structured ASCII header encoding metadata such as sample rate, channel count, encoding type, speaker demographics, and transcription annotations — making it ideal for distributing speech corpora. NIST files typically store uncompressed PCM or mu-law audio at telephone-quality sample rates (8 kHz or 16 kHz), though the container is flexible enough to hold various encodings. A key advantage is the rich self-documenting header that lets researchers embed detailed corpus metadata directly in the file, eliminating sidecar files. SPHERE has also become the de facto standard for major speech databases like TIMIT, Switchboard, and the Fisher corpus, ensuring broad recognition across academic and government labs. The open specification and availability of command-line tools (sphere, h_strip, w_decode) make it straightforward to convert, inspect, and process these files programmatically in speech processing pipelines.
Initial release: 1990

Frequently Asked Questions

Why convert AU to NIST?

AU files are tied to UNIX and Java ecosystems. Converting to NIST makes your audio accessible on any platform.

What opens NIST audio?

You can play NIST using NIST SPHERE utilities, SoX, Audacity. It works out of the box on most systems with standard audio software.

Does converting AU to NIST affect quality?

Lossless-to-lossless conversions preserve all audio data. When the target uses lossy compression, some quality reduction is inherent in the codec.

Does the converter support batch AU conversion?

Absolutely. You can upload a batch of AU files and convert them all to NIST together, saving significant time on large collections.

Is the AU to NIST conversion secure?

Completely. Your AU files are erased immediately after processing, and converted NIST results are purged from our servers within 24 hours.