Fine-tuning Whisper with Spontaneous Persian Speech (SPS)
Summary
Most Persian speech corpora, such as FARSDAT and Mozilla Common Voice, contain read speech. As a result, ASR systems handle informal Persian poorly, especially hesitations, overlapping turns and discourse markers. The authors address this gap with the Spontaneous Persian Speech (SPS) dataset, built from YouTube videos in which two or three young speakers with a Tehrani accent chat in places ranging from studios to cars and shops. They used a semi-automatic workflow:
- OpenAI's Whisper produced the first transcripts as .srt files.
- The pysrt library converted these to TextGrid format.
- A native speaker corrected the timestamps, spelling and punctuation in Praat.
The resulting corpus has roughly 11 hours of audio. The authors tested off-the-shelf Whisper on a 70-minute portion and found very high error rates, often involving consonants with similar articulation. They attribute this to missing informal register in Whisper's training data. Fine-tuning the small and medium Whisper models on SPS substantially lowered WER. The work suggests that even a modest corpus targeted at one domain can meaningfully strengthen ASR for an under-resourced, diglossic language.
Key points
- SPS contains 694 minutes of audio from 65 speakers (34 male, 31 female), totalling 526,585 tokens. Speakers are aged 20–30 and recorded in quiet and noisy environments.
- Segments last 1.24–3.25 s and hold about 3–9 words, averaging 5.01 words per interval. Lexical diversity (TTR) is 0.352.
- Baseline WER on 70 minutes of SPS was 88.72% for Whisper small, 83.10% for medium and 49.04% for large (large-v3). Typical errors include /d/→/t/ and /z/→/s/ substitutions and dropped words.
- Once fine-tuned on SPS, the small and medium models each showed a marked drop in WER. The provided text omits the exact post-fine-tuning figures.
- The dataset is for non-commercial research use only. It will not be shared publicly until YouTube channel owners give consent, and it would also need anonymization, since speakers mention their full names.
Institutions
Cite
Cite as Behnoosh Namdarzadeh and Nicolas Ballier. 2026. Fine-tuning Whisper with Spontaneous Persian Speech (SPS). Proceedings of the SIGUL 2026 Joint Workshop with ELE, EURALI, and DCLRL: Towards Inclusivity and Equality: Language Resources and Technologies for Under-Resourced and Endangered Languages.
@inproceedings{namdarzadeh2026fine,
title = {{Fine-tuning Whisper with Spontaneous Persian Speech (SPS)}},
author = {Behnoosh Namdarzadeh and Nicolas Ballier},
booktitle = {Proceedings of the SIGUL 2026 Joint Workshop with ELE, EURALI, and DCLRL: Towards Inclusivity and Equality: Language Resources and Technologies for Under-Resourced and Endangered Languages},
year = {2026},
doi = {10.63317/2ca2yoj8fzgd},
url = {https://doi.org/10.63317/2ca2yoj8fzgd}
}References
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