LibriSpeech
LibriSpeech is the reference dataset for English automatic speech recognition (ASR, turning spoken audio into text). It draws on LibriVox, a collection of volunteer-read public domain audiobooks, and pairs the audio with sentence-level transcripts so models can learn the mapping from sound to words.
The corpus is split into training, development, and test sets, with clean and noisier subsets so you can measure how a model holds up in harder conditions. Audio is stored as FLAC (a lossless open format), and the whole set totals around 1,000 hours. It remains the most common yardstick for reporting English ASR accuracy in research papers.
Related sources
LJ Speech
An open dataset of 13,100 short audio clips of a single speaker reading passages from seven non-fiction books. Every clip is transcribed and clips run from 1 to 10 seconds. Released into the public domain, it is the standard single-speaker text-to-speech benchmark.
Mozilla Common Voice
A crowdsourced speech platform from Mozilla that releases datasets under the CC0 licence. Volunteers read sentences aloud and other community members validate each recording. As of release 19.0 it holds 32,584 hours of speech across 131 languages, making it one of the largest openly licensed voice datasets available.
OpenSLR
Open Speech and Language Resources, a hosting site for speech and language datasets, software, and models. It is the home of LibriSpeech and dozens of other language-specific speech corpora, making it a central catalogue for finding openly available voice data.
The People's Speech
A large, freely licensed English speech recognition dataset from MLCommons, assembled from openly licensed sources and totalling more than 30,000 hours. Built as a permissively licensed alternative for training commercial automatic speech recognition systems.