Apple Researchers Propose Lightweight Code-Switching Detection Using Speech Foundation Models

·2026.10.14 09:00

Key point

The method achieves a mean F1 score of 0.798 across 14 language pairs in CS-FLEURS using the Whisper-small encoder.

Details

Apple researchers have developed a lightweight method to detect code-switching (CS) directly from speech, addressing the underrepresentation of multilingual alternation in pretraining corpora. The approach leverages frame-level language information in pretrained speech encoders to identify whether both languages are present within a single utterance, bypassing the need for accurate multilingual transcriptions.

Methodology

The technique identifies language-selective hidden-state dimensions using monolingual recordings and aggregates their frame-level activations to generate a CS prediction. A small CS set is used to tune the decision rule, allowing the system to function without heavy computational overhead.

Performance Results

When tested on the CS-FLEURS dataset, the Whisper-small encoder achieved a mean F1 score of 0.798 across 14 language pairs. This performance surpasses baseline models, including:

  • A CNN baseline with an F1 of 0.776
  • A HuBERT linear baseline trained for monolingual language identification with an F1 of 0.751

The findings indicate that pretrained speech encoders already contain sufficient information to identify CS utterances, offering a practical tool for constructing more representative multilingual datasets.

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