Skip to content
DSML.KZ
Publications

Article · Applied Sciences · November 7, 2026

Vowel-Harmony Constraints in Kazakh ASR: A Systematic Investigation of Integration Approaches

Mussa Turdalyuly, Aigerim Yerimbetova, Akbayan Bekarystankyzy, Дина Оралбекова, Tolganay Turdalykyzy, Bekturgan Akhmetov

Akbayan Bekarystankyzy
Open via DOI

Abstract

Kazakh vowel harmony is well established linguistically, but its explicit integration into modern neural automatic speech recognition (ASR) remains insufficiently studied. This work investigates whether a productive front/back vowel-harmony constraint can be operationalized within Whisper large-v3 for Kazakh ASR. Two complementary strategies are evaluated on the ISSAI Kazakh Speech Corpus 2: (1) a differentiable token-level harmony regularizer added during fine-tuning and (2) harmony-based N-best hypothesis re-ranking during inference. We further introduce the Harmony Violation Rate (HVR) as a diagnostic measure and analyze Whisper’s byte-level BPE representation of Kazakh vowels. Neither integration strategy produces a statistically significant improvement in test WER. Re-ranking yields a small but statistically significant reduction in HVR, while additional analyses show no recognition disadvantage for byte-fragmented vowels and no systematic reduction in front/back vowel confusions after harmony-constrained fine-tuning. These findings show that simple token-level regularization and sentence-level re-ranking do not adequately model the contextual stem–suffix dependency underlying Kazakh vowel harmony. The study therefore identifies specific limitations of straightforward phonological-constraint integration and provides diagnostic evidence for future representation- and morphology-aware Kazakh ASR.

Speech Recognition and SynthesisPhonetics and Phonology ResearchSpeech and Audio Processingspeech recognitionWhisperbyte pair encoding

More by Akbayan Bekarystankyzy