WAV to SPH Converter

Produce SPHERE speech research audio from WAV files

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Ideal Source Format

Uncompressed WAV is the best source for SPHERE speech corpora — artifact-free research data.

Corpus Standard

SPH is what major speech toolkits expect — produce from uncompressed WAV.

Dataset Processing

Convert full WAV collections to SPH simultaneously.

How to convert WAV to SPH

1

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

2

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

3

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

About formats

WAV (Waveform Audio File Format) is an uncompressed audio container jointly developed by Microsoft and IBM, first published in August 1991 alongside Windows 3.1. Built on the Resource Interchange File Format (RIFF), WAV stores audio data — most commonly as linear pulse-code modulation (LPCM) — together with metadata describing sample rate, bit depth, and channel count. This straightforward structure has made WAV the de facto standard for uncompressed audio on Windows and a universally accepted interchange format across virtually every operating system, audio editor, and media player in existence. CD-quality WAV files use 16-bit samples at 44.1 kHz stereo, while professional workflows routinely employ 24-bit or 32-bit float samples at rates up to 192 kHz. A major advantage is zero-loss fidelity: because standard WAV applies no compression, the stored data is an exact digital representation of the original recording, making it the preferred choice for mastering and archiving. WAV also supports embedded metadata through INFO and BWF chunks, enabling timestamping and production notes. The main trade-off is file size — one minute of CD-quality stereo occupies roughly 10 MB — and the 32-bit RIFF structure imposes a 4 GB limit, though RF64 removes that ceiling.
Developer: Microsoft and IBM
Initial release: August 1991
SPH is the file extension for audio stored in the NIST SPHERE (SPeech HEader REsources) format, a standard created by the U.S. National Institute of Standards and Technology around 1990. Built for speech research, SPH files carry a 1024-byte ASCII header packed with metadata — database identifiers, channel counts, sample rates, byte ordering, and compression type — making every recording self-describing. The underlying audio is typically 16-bit linear PCM sampled at 16 kHz, though other configurations are permitted. Researchers at NIST, DARPA, and universities worldwide rely on SPH for distributing speech corpora such as TIMIT, Switchboard, and the LDC collections that underpin modern automatic speech recognition systems. A key advantage is that the human-readable header lets scripts parse recording metadata without binary decoding. The format's strict standardization also eliminates ambiguity when sharing datasets across institutions and platforms. Because SPH files store uncompressed PCM, they preserve full audio fidelity — critical when training acoustic models where even small artifacts can skew results.
Initial release: 1990

Frequently Asked Questions

Why convert WAV to SPH?

SPH (SPHERE) is the NIST standard for speech corpora. Uncompressed WAV is the gold standard source for research data.

What uses SPH?

Kaldi, HTK, NIST evaluation tools, and academic speech datasets use SPHERE format.

Is SPH the same as NIST?

Yes — both refer to SPHERE defined by the National Institute of Standards and Technology.

Is the conversion lossless?

SPH supports PCM — WAV to SPH preserves audio data without loss.

Can I convert a dataset?

Upload your entire WAV speech collection and produce SPH for every file at once.

WAV to SPH Quality Rating

4.9 (21 votes)
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