Towards Interpretability of Automatic Phoneme Analysis in Cleft Lip and Palate Speech

Cleft Lip and Palate ranks among the most common congenital abnormalities and significantly influences speech articulation, resulting in varying phonemic impacts. In a clinical context, a detailed diagnosis is carried out by time-consuming perceptual evaluations. We use perceptual ratings of different articulatory modifications on phoneme-level as ground-truth and propose a system based on wav2vec 2.0, trained to the downstream task of classifying phonemic criteria as a multi-class and multi-label problem. The system is trained for detection on utterance level, without the usage of phoneme labels. To gain a clearer understanding of which areas of the speech signal have the greatest impact on classification, we assess the extent to which our system aligns with expert ratings at the phoneme level. Additionally, we examine which specific phonemes play a decisive role in determining the final classification of the labeled criteria. The results show that salient phonemes marked by experts contribute remarkably greater to the classification of the correct class using feature relevance explanation methods. To the best of our knowledge, this is the first study incorporating various utterance-level articulatory modifications classification and phoneme-level interpretation, offering a more comprehensive understanding for potential clinical applications.