Model Details
Model Description
- Developed by: thunderboltc
- Model type: Whisper Small (Encoder-Decoder Transformer, Seq2Seq)
- Language: Santali (
sat) — transcribed in custom Roman transliteration (Sanlish)
- Base model: openai/whisper-small
- Parameters: 241,734,912 (~242M)
- Fine-tuned for: Low-resource ASR — Santali speech to Sanlish text
- License: MIT
What is Sanlish?
Sanlish is a custom Roman-script transliteration of Santali designed to bridge the gap between Santali phonetics and Latin-alphabet-based ASR systems. It was developed as part of this thesis to serve as an intermediate representation between Santali audio and Bangla translation.
Training Details
Training Data
- Dataset: 502 Santali audio recordings with parallel Sanlish transliteration annotations
- Collected by: thunderboltc (thesis dataset, not yet publicly released)
- Split:
Table with columns: Split, Size, Percentage| Split | Size | Percentage |
|---|
| Train | 401 | 80% |
| Validation | 50 | 10% |
| Test | 51 | 10% |
- Audio format: WAV, 16kHz mono
- Text target: Custom Roman transliteration (Sanlish)
Training Procedure
Preprocessing
- Audio resampled to 16,000 Hz
- Log-mel spectrogram features extracted using WhisperFeatureExtractor (80 mel bins, 3000 frames)
- Text tokenized using WhisperTokenizer with
language=english, task=transcribe
forced_decoder_ids and suppress_tokens disabled to allow custom vocabulary transcription
Training Hyperparameters
Table with columns: Parameter, Value| Parameter | Value |
|---|
| Epochs | 25 |
| Learning Rate | 1e-5 |
| Batch Size (per device) | 8 |
| Gradient Accumulation Steps | 2 (effective batch = 16) |
| Warmup Steps | 50 |
| Precision | fp16 mixed precision |
| Evaluation Strategy | Per epoch |
| Best Model Selection | Lowest validation WER |
| Hardware | NVIDIA Tesla T4 (Google Colab) |
Best Checkpoint
Epoch 13 was selected as the best checkpoint based on lowest validation WER (53.41%).
Evaluation
Results on Test Set (51 utterances)
Table with columns: Metric, Value| Metric | Value |
|---|
| Word Error Rate (WER) | 56.55% |
| Character Error Rate (CER) | 13.31% |
These results are consistent with expectations for a low-resource ASR system trained on ~400 utterances. The large gap between WER and CER reflects that the model captures phonetic character structure well, even when full word sequences deviate from the reference.
Sample Predictions
Table with columns: Reference, Prediction| Reference | Prediction |
|---|
| onde alom chala a | onde alom chala a ✓ |
| tehindo adi raashkaien yaikaoda | tehindo adi reskaien yaikaoda |
| gapa shetah ale saote baskiyago meh | gapa setah ale saote baskiyago meh |
| shetay bhuh da | shetay bhuheda |
How to Get Started
import torch
from transformers import WhisperProcessor, WhisperForConditionalGeneration
import librosa
processor = WhisperProcessor.from_pretrained("thunderboltc/whisper-small-santali-sanlish")
model = WhisperForConditionalGeneration.from_pretrained("thunderboltc/whisper-small-santali-sanlish")
audio, sr = librosa.load("your_santali_audio.wav", sr=16000)
inputs = processor.feature_extractor(audio, sampling_rate=16000, return_tensors="pt")
with torch.no_grad():
predicted_ids = model.generate(inputs.input_features)
transcription = processor.tokenizer.batch_decode(predicted_ids, skip_special_tokens=True)
print("Sanlish transcription:", transcription[0])
Intended Use
Direct Use
Transcribing Santali speech into Sanlish (custom Roman transliteration) for downstream NLP tasks.
Downstream Use
This model is designed to feed into a Machine Translation (MT) model (NLLB-200) for end-to-end Santali Speech → Bangla Text translation.
Out-of-Scope Use
- Not suitable for general-purpose ASR in other languages
- Not recommended for standard Santali Ol Chiki script transcription
- Performance may degrade on speaker accents or recording conditions not represented in the 502-utterance training set
Limitations & Bias
- Trained on only 502 utterances — a very small dataset by ASR standards
- May not generalize well to unseen speakers or recording environments
- Sanlish transliteration scheme has inherent inconsistencies (word boundary variation, hyphenation) which inflate WER beyond true phonetic error rate
- No speaker diversity information available for the training set
Citation
If you use this model in your research, please cite:
@misc{thunderboltc2025whisper-santali,
author = {thunderboltc},
title = {Whisper Small Fine-tuned on Santali Custom Transliteration (Sanlish)},
year = {2025},
publisher = {Hugging Face},
url = {https://huggingface.co/thunderboltc/whisper-small-santali-sanlish}
}
Environmental Impact
- Hardware: NVIDIA Tesla T4
- Cloud Provider: Google Colab
- Hours used: ~1.25 hours
- Carbon emissions: Estimated using the ML Impact Calculator