Automatic speech recognition (ASR) for dysarthric speech is challenging. The acoustic characteristics of dysarthric speech are highly variable and there are often fewer distinguishing cues between phonetic tokens. Multimodal ASR utilises the data from other modalities to facilitate the task when a single acoustic modality proves insufficient. Articulatory information, which encapsulates knowledge about the speech production process, may constitute such a complementary modality. Although multimodal acoustic-articulatory ASR has received increasing attention recently, incorporating real articulatory data is under-explored for dysarthric speech recognition. This paper investigates the effectiveness of multimodal acoustic modelling using real dysarthric speech articulatory information in combination with acoustic features, especially raw signal representations which are more informative than classic features, leading to learning representations tailored to dysarthric ASR. In particular, various raw acoustic-articulatory multimodal dysarthric speech recognition systems are developed and compared with similar systems with hand-crafted features. Furthermore, the difference between dysarthric and typical speech in terms of articulatory information is systematically analysed by using a statistical space distribution indicator called Maximum Articulator Motion Range (MAMR). Additionally, we used mutual information analysis to investigate the robustness and phonetic information content of the articulatory features, offering insights that support feature selection and the ASR results. Experimental results on the widely used TORGO dysarthric speech dataset show that combining the articulatory and raw acoustic features at the empirically found optimal fusion level achieves a notable performance gain, leading to up to 7.6% and 12.8% relative word error rate (WER) reduction for dysarthric and typical speech, respectively. ... Read more

Speech technologies have advanced significantly, yet they remain largely trained on typical speech, limiting their applicability to individuals with speech and language impairments. A key obstacle is the lack of well-annotated and representative atypical speech corpora. This paper conducts a multi-project survey and shares the first-hand experience on the challenges of collecting, annotating, using, and sharing atypical speech data. Experiences from seven research projects on collecting atypical speech data, involving both academic and clinical perspectives, are reported and potential issues are discussed. Furthermore, the paper provides practical guidelines that allow for standardisation and harmonisation of data collection practices, which are crucial to allow studies to be compared, replicated, and validated, which is essential for developing more inclusive and effective speech technologies. ... Read more

Automatic dysarthric speech recognition (ADSR) remains challenging due to the irregularities in speech caused by motor control impairments and the limited availability of dysarthric speech data. This paper explores the integration of articulatory features, captured using Electromagnetic Articulography (EMA), with both conventional acoustic features and those extracted from large-scale pretrained models including Whisper and XLSR-53 as well as the fine-tuned Whisper model. We propose end-to-end (E2E) Conformer-based acoustic-articulatory models for ADSR and compare their performance against the corresponding hybrid TDNNF models. The experimental results show that using the fine-tuned Whisper features (Whisper-FT) fused with articulatory features achieves the lowest (10.5%) word error rate (WER) on dysarthric speech, with particularly significant improvements for severely dysarthric speech, reaching a WER of 20.8%. ... Read more

Dysarthric speech poses significant challenges for automatic speech recognition (ASR) systems due to its high variability and reduced intelligibility. In this work we explore the use of diffusion models for dysarthric speech enhancement, which is based on the hypothesis that using diffusion-based speech enhancement moves the distribution of dysarthric speech closer to that of typical speech, which could potentially improve dysarthric speech recognition performance. We assess the effect of two diffusion-based and one signal-processing-based speech enhancement algorithms on intelligibility and speech quality of two English dysarthric speech corpora. We applied speech enhancement to both typical and dysarthric speech and evaluate the ASR performance using Whisper-Turbo, and the subjective and objective speech quality of the original and enhanced dysarthric speech. We also fine-tuned Whisper-Turbo on the enhanced speech to assess its impact on recognition performance. ... Read more

State-of-the-art ASRs show suboptimal performance for child speech. The scarcity of child speech limits the development of child speech recognition (CSR). Therefore, we studied child-to-child voice conversion (VC) from existing child speakers in the dataset and additional (new) child speakers via monolingual and cross-lingual (Dutch-to-German) VC, respectively. The results showed that cross-lingual child-to-child VC significantly improved child ASR performance. Experiments on the impact of the quantity of child-to-child cross-lingual VC-generated data on fine-tuning (FT) ASR models gave the best results with two-fold augmentation for our FT-Conformer model and FT-Whisper model which reduced WERs with ~3% absolute compared to the baseline, and with six-fold augmentation for the model trained from scratch, which improved by an absolute 3.6% WER. Moreover, using a small amount of "high-quality" VC-generated data achieved similar results to those of our best-FT models. ... Read more

In this paper, we explore the effectiveness of deploying the raw phase and magnitude spectra for dysarthric speech recognition, detection and classification. In particular, we scrutinise the usefulness of various raw phase-based representations along with their combinations with the raw magnitude spectrum and filterbank features. We employed single and multi-stream architectures consisting of a cascade of convolutional, recurrent and fully-connected layers for acoustic modelling. Furthermore, we investigate various configurations and fusion schemes as well as their training dynamics. In addition, the accuracies of the raw phase and magnitude based systems in the detection and classification tasks are studied and discussed. We report the performance on the UASpeech and TORGO dysarthric speech databases and for different severity levels. Our best system achieved WERs of 31.2% and 9.1% for dysarthric and typical speech on TORGO and 30.2% on UASpeech, respectively. ... Read more

Automatic speech recognition (ASR) should serve every speaker, not only the majority “standard” speakers of a language. In order to build inclusive ASR, mitigating the bias against speaker groups who speak in a “non-standard” or “diverse” way is crucial. We aim to mitigate the bias against non-native-accented Flemish in a Flemish ASR system. Since this is a low-resource problem, we investigate the optimal type of data augmentation, i.e., speed/pitch perturbation, cross-lingual voice conversion-based methods, and SpecAugment, applied to both native Flemish and non-native-accented Flemish, for bias mitigation. The results showed that specific types of data augmentation applied to both native and non-native-accented speech improve non-native-accented ASR while applying data augmentation to the non-native-accented speech is more conducive to bias reduction. Combining both gave the largest bias reduction for human-machine interaction (HMI) as well as read-type speech. ... Read more