---
license: cc-by-4.0
language:
- en
pretty_name: LibriSpeech Segment
task_categories:
- automatic-speech-recognition
tags:
- speech
- phone-alignment
- segmentation
- english
size_categories:
- 100K<n<1M
---

# LibriSpeech Segment

English read-speech corpus with **phone-level time alignments** (Montreal
Forced Aligner). Suitable for training and evaluating phone recognition and
phonetic segmentation models.

## Sources

- **Audio**: [LibriSpeech](https://www.openslr.org/12/) (OpenSLR 12) by
  Vassil Panayotov, Guoguo Chen, Daniel Povey, Sanjeev Khudanpur (2015).
- **Phone alignments**:
  [`anyspeech/librispeech_MFA_alignments`](https://huggingface.co/datasets/anyspeech/librispeech_MFA_alignments).

## Splits

| Split             | Utterances |
|-------------------|------------|
| train.clean.100   | 28,538     |
| train.clean.360   | 104,008    |
| train.other.500   | 148,645    |
| dev.clean         | 2,703      |
| dev.other         | 2,864      |
| test.clean        | 2,620      |
| test.other        | 2,938      |

Split labels follow the LibriSpeech canonical naming.

## Schema

| Column         | Type                 | Description                                          |
|----------------|----------------------|------------------------------------------------------|
| `utt_id`       | string               | Utterance id, e.g. `7635-105409-0022`                |
| `audio`        | Audio(16 kHz)        | Embedded waveform bytes (decoded on access)          |
| `text`         | string               | Word-level transcript (uppercase)                    |
| `phones`       | sequence[string]     | ARPABET phone tokens                                 |
| `phone_starts` | sequence[float64]    | Phone start times in seconds                         |
| `phone_ends`   | sequence[float64]    | Phone end times in seconds                           |
| `language`     | string               | `eng` (ISO 639-3)                                    |
| `speaker_id`   | string               | LibriSpeech speaker id                               |
| `duration`     | float64              | Utterance duration in seconds                        |
| `split`        | string               | LibriSpeech split label                              |

## Phone inventory

Phones are ARPABET (e.g. `DH`, `EH`, `R`, `AE`, `OW`). Silence and pauses
are marked with `[SIL]` intervals, kept in the alignment so boundary models
can learn from them. `[UNK]` may also appear for OOV cases.

## License

Released under the **CC BY 4.0** license, matching the original LibriSpeech
audio.

## Citation

```bibtex
@inproceedings{panayotov2015librispeech,
  title={Librispeech: an asr corpus based on public domain audio books},
  author={Panayotov, Vassil and Chen, Guoguo and Povey, Daniel and Khudanpur, Sanjeev},
  booktitle={2015 IEEE international conference on acoustics, speech and signal processing (ICASSP)},
  pages={5206--5210},
  year={2015},
  organization={IEEE}
}
```