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O.E. Scharenborg

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Current state-of-the-art automatic speech recognition (ASR) systems recognize typical speech (very) well. However, recent research has shown that their performance degrades for “diverse” speech, i.e., speech that diverges from “typical” speech due to, among others, demographic and sociolinguistic factors. In this work, given the rapid development of ASR technologies, we examined the performance of nine recently released ASR systems developed by Google, Microsoft, Meta, NVIDIA, and OpenAI, and three custom ASR models trained from scratch, on Dutch diverse speech. Our results showed that although overall recognition results differ quite substantially between the different systems, all systems show similar patterns regarding recognition performance for diverse speaker groups: for most ASR systems and models, language proficiency differences and severe speech motor impairment had a greater impact on performance disparities between speaker groups than demographic or sociolinguistic factors, indicating that acoustic variability due to demographic and sociolinguistic factors is well-represented in “typical speech” training data and consequently is well-modeled in the models. Furthermore, we found that differences in data processing pipelines and decoding setups significantly influenced recognition performance. Importantly, updates to company-developed ASR systems do not always improve performance of or reduce performance disparities between diverse speaker groups. ...
Journal article (2025) - Marija Stepanović, Christian Hardmeier, Odette Scharenborg
Multilingual phone recognition models can learn language-independent pronunciation patterns from large volumes of spoken data and recognize them across languages. This potential can be harnessed to improve speech technologies for underresourced languages. However, these models are typically trained on phonological representations of speech sounds, which do not necessarily reflect the phonetic realization of speech. A mismatch between a phonological symbol and its phonetic realizations can lead to phone confusions and reduce performance. This work introduces formant-based vowel categorization aimed at improving cross-lingual vowel recognition by uncovering a vowel's phonetic quality from its formant frequencies, and reorganizing the vowel categories in a multilingual speech corpus to increase their consistency across languages. The work investigates vowel categories obtained from a trilingual multi-dialect speech corpus of Danish, Norwegian, and Swedish using three categorization techniques. Cross-lingual phone recognition experiments reveal that uniting vowel categories of different languages into a set of shared formant-based categories improves cross-lingual recognition of the shared vowels, but also interferes with recognition of vowels not present in one or more training languages. Cross-lingual evaluation on regional dialects provides inconclusive results. Nevertheless, improved recognition of individual vowels can translate to improvements in overall phone recognition on languages unseen during training. ...
Conference paper (2025) - D. de Groot, B. Karslioglu, O. Scharenborg, J. Martinez
In this paper we propose a robust loudspeaker beamforming algorithm which is used to enhance the performance of voice driven applications in scenarios where the loudspeakers introduce the majority of the noise, e.g. when music is playing loudly. The loudspeaker beamformer modifies the loudspeaker playback signals to create a low-acoustic-energy region around the device that implements automatic speech recognition for a voice driven application (VDA). The algorithm utilises a distortion measure based on human auditory perception to limit the distortion perceived by human listeners. Simulations and real-world experiments show that the proposed loudspeaker beamformer improves the speech recognition performance in all tested scenarios. Moreover, the algorithm allows to further reduce the acoustic energy around the VDA device at the expense of reduced objective audio quality at the listener’s location ...
Conference paper (2025) - Zhengjun Yue, Mara Barberis, Tanvina Patel, Judith Dineley, Willemijn Doedens, Lottie Stipdonk, Yuanyuan Zhang, Elke De Witte, Odette Scharenborg, More authors...
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. ...
Journal article (2025) - Terry Amorese, Marialucia Cuciniello, Anna Alterio, Daniele Pepe, Odette Scharenborg, Gennaro Cordasco, Anna Esposito
Introduction: This work aims to understand the contextual factors affecting speech emotion recognition (SER), more specifically the current research investigates whether the identification of vocal emotional expressions of anger, fear, sadness, joy, and neutrality is affected by three factors: (a) the experimental setting, exploring vocal emotion recognition in both a controlled, soundproof laboratory and a more natural listening environment; (b) the effect of stimuli’s background noise: sentences were presented with three different levels of noise to gradually increase the level of difficulty: one clear (no noise) condition and two noise conditions; (c) language familiarity, since the stimuli comprised Italian sentences, and participants were both native (Italians) and Dutch speakers, who did not know Italian. Method: Dutch and Italian participants were involved in a vocal emotion recognition task carried out in two different experimental settings (realistic vs. laboratory). The stimuli were vocal utterances from the Italian EMOVO dataset, conveying emotions like anger, fear, sadness, joy, and neutrality, and were presented in three different noise conditions. Results: Concerning the effect of the experimental setting, even in higher levels of background noise conditions, individuals possess the remarkable ability to discern emotional nuances conveyed through voice. Regarding familiarity with the language, differences in emotion recognition performance between the Italian and Dutch listeners were observed, but the error magnitude was contingent on the emotional categories. Higher noise levels reduced accuracy, but people could still discern emotions, especially prosody. Conclusion: The study highlighted that emotion recognition is influenced by variables such as listening context, background noise, and language familiarity. These results could be useful for developing robust Speech Emotion Recognition (SER) systems and improving human-computer interaction. ...
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. ...
Conference paper (2025) - Marialucia Cuciniello, Terry Amorese, Anna Alterio, Daniele Pepe, Anna Esposito, Odette Scharenborg, Gennaro Cordasco
This study investigates the impact of stimulus gender on vocal emotion recognition. To that end, 3 groups of listeners were asked to classify joy, neutral state, fear, anger and sadness in Italian meaningful and nonsensical sentences in 2 settings: a controlled laboratory setting to which a group of Dutch listeners was assigned and a naturalistic setting to which 2 groups respectively of Dutch and Italian listeners were assigned. Two levels of background noise were applied to the sentences to increase the level of task difficulty. Results showed an impact of stimulus gender on emotion classification performance, which seemed dependent on the emotion category: anger was better recognized when spoken by male speakers in both experimental settings, while joy was better recognized when spoken by female speakers by Dutch listeners in the laboratory and Italian listeners in the naturalistic setting, and fear was better recognized when spoken by female speakers in the naturalistic setting. ...
Conference paper (2024) - Y. Zhang, Z. Yue, T.B. Patel, O.E. Scharenborg
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. ...

Using GPT-4 Annotation For An Efficient And Fast Dataset Creation Pipeline

Conference paper (2024) - Maliha Jahan, Helin Wang, Thomas Thebaud, Yinglun Sun, Giang Le, Zsuzsanna Fagyal, Odette Scharenborg, Mark Hasegawa-Johnson, Laureano Moro-Velazquez, Najim Dehak
The growing emphasis on fairness in speech-processing tasks requires datasets with speakers from diverse subgroups that allow training and evaluating fair speech technology systems. However, creating such datasets through manual annotation can be costly. To address this challenge, we present a semi-automated dataset creation pipeline that leverages large language models. We use this pipeline to generate a dataset of speakers identifying themself or another speaker as belonging to a particular race, ethnicity, or national origin group. We use OpenaAI's GPT-4 to perform two complex annotation tasks- separating files relevant to our intended dataset from the irrelevant ones (filtering) and finding and extracting information on identifications within a transcript (tagging). By evaluating GPT-4's performance using human annotations as ground truths, we show that it can reduce resources required by dataset annotation while barely losing any important information. For the filtering task, GPT-4 had a very low miss rate of 6.93%. GPT-4's tagging performance showed a trade-off between precision and recall, where the latter got as high as 97%, but precision never exceeded 45%. Our approach reduces the time required for the filtering and tagging tasks by 95% and 80%, respectively. We also present an in-depth error analysis of GPT-4's performance. ...
Journal article (2024) - T.B. Patel, O.E. Scharenborg
Children’s Speech Recognition (CSR) is a challenging task due to the high variability in children’s speech patterns and limited amount of available annotated children’s speech data. We aim to improve CSR in the often-occurring scenario that no children’s speech data is available for training the Automatic Speech Recognition (ASR) systems. Traditionally, Vocal Tract Length Normalization (VTLN) has been widely used in hybrid ASR systems to address acoustic mismatch and variability in children’s speech when training models on adults’ speech. Meanwhile, End-to-End (E2E) systems often use data augmentation methods to create child-like speech from adults’ speech. For adult speech-trained ASRs, we investigate the effectiveness of augmentation methods; speed perturbations and spectral augmentation, along with VTLN, in an E2E framework for the CSR task, comparing these across Dutch, German, and Mandarin. We applied VTLN at different stages (training/test) of the ASR and conducted age and gender analyses. Our experiments showed highly similar patterns across the languages: Speed Perturbations and Spectral Augmentation yield significant performance improvements, while VTLN provided further improvements while maintaining recognition performance on adults’ speech (depending on when it is applied). Additionally, VTLN showed performance improvement for both male and female speakers and was particularly effective for younger children. ...
Conference paper (2024) - Chris Bras, Tanvina Patel, Odette Scharenborg
Brain-Computer Interfaces (BCIs) open avenues for communication among individuals unable to use voice or gestures. Silent speech interfaces are one such approach for BCIs that could offer a transformative means of connecting with the external world. Performance on imagined speech decoding however is rather low due to, amongst others, data scarcity and the lack of a clear starting and end point of the imagined speech in the brain signal. We investigate whether using electroencephalography (EEG) signals from articulated speech can be used to improve imagined speech decoding in two ways: we investigate whether articulated speech EEG signals can be used to predict the end point of the imagined speech and use the articulated speech EEG as extra training data for speaker-independent imagined vowel classification. Our results show that using EEG data from articulated speech did not improve classification of vowels in imagined speech, probably due to high variability in EEG signals amongst speakers. ...
Practice and recent evidence show that state-of-the-art (SotA) automatic speech recognition (ASR) systems do not perform equally well for all speaker groups. Many factors can cause this bias against different speaker groups. This paper, for the first time, systematically quantifies and finds speech recognition bias against gender, age, regional accents and non-native accents, and investigates the origin of this bias by investigating bias cross-lingually (i.e., Dutch and Mandarin) and for two different SotA ASR architectures (a hybrid DNN-HMM and an attention based end-to-end (E2E) model) through a phoneme error analysis. The results show that only a fraction of the bias can be explained by pronunciation differences between speaker groups, and that in order to mitigate bias, language- and architecture specific solutions need to be found. ...
Conference paper (2023) - Thomas Wilschut, Florian Sense, Odette Scharenborg, Hedderik van Rijn
Cognitive models of memory retrieval aim to describe human learning and forgetting over time. Such models have been successfully applied in digital systems that aid in memorizing information by adapting to the needs of individual learners. The memory models used in these systems typically measure the accuracy and latency of typed retrieval attempts. However, recent advances in speech technology have led to the development of learning systems that allow for spoken inputs. Here, we explore the possibility of improving a cognitive model of memory retrieval by using information present in speech signals during spoken retrieval attempts. We asked 44 participants to study vocabulary items by spoken rehearsal, and automatically extracted high-level prosodic speech features—patterns of stress and intonation—such as pitch dynamics, speaking speed and intensity from over 7,000 utterances. We demonstrate that some prosodic speech features are associated with accuracy and response latency for retrieval attempts, and that speech feature informed memory models make better predictions of future performance relative to models that only use accuracy and response latency. Our results have theoretical relevance, as they show how memory strength is reflected in a specific speech signature. They also have important practical implications as they contribute to the development of memory models for spoken retrieval that have numerous real-world applications. ...
Conference paper (2023) - YuanYuan Zhang, Aaricia Herygers, Tanvina Patel, Zhengjun Yue, Odette Scharenborg
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. ...
Conference paper (2023) - Aaricia Herygers, Vass Verkhodanova, Matt Coler, O.E. Scharenborg, Munir Georges
Research has shown that automatic speech recognition (ASR) systems exhibit biases against different speaker groups, e.g., based on age or gender. This paper presents an investigation into bias in recent Flemish ASR. Seeing as Belgian Dutch, which is also known as Flemish, is often not included in Dutch ASR systems, a state-of-the-art ASR system for Dutch is trained using the Netherlandic Dutch data from the Spoken Dutch Corpus. Using the Flemish data from the JASMIN-CGN corpus, word error rates for various regional variants of Flemish are then compared. In addition, the most misrecognized phonemes are compared across speaker groups. The evaluation confirms a bias against speakers from West Flanders and Limburg, as well as against children, male speakers, and non-native speakers. ...

Synchronized Speech and Talking Head Generation for Arbitrary Persons

Journal article (2023) - Xinsheng Wang, Qicong Xie, Lei Xie, Jihua Zhu, Odette Scharenborg
Automatically generating videos in which synthesized speech is synchronized with lip movements in a talking head has great potential in many human-computer interaction scenarios. In this paper, we present an automatic method to generate synchronized speech and talking-head videos on the basis of text and a single face image of an arbitrary person as input. In contrast to previous text-driven talking head generation methods, which can only synthesize the voice of a specific person, the proposed method is capable of synthesizing speech for any person. Specifically, the proposed method decomposes the generation of synchronized speech and talking head videos into two stages, i.e., a text-to-speech (TTS) stage and a speech-driven talking head generation stage. The proposed TTS module is a face-conditioned multi-speaker TTS model that gets the speaker identity information from face images instead of speech, which allows us to synthesize a personalized voice on the basis of the input face image. To generate the talking head videos from the face images, a facial landmark-based method that can predict both lip movements and head rotations is proposed. Extensive experiments demonstrate that the proposed method is able to generate synchronized speech and talking head videos for arbitrary persons, in which the timbre of the synthesized voice is in harmony with the input face, and the proposed landmark-based talking head method outperforms the state-of-the-art landmark-based method on generating natural talking head videos. ...
Journal article (2023) - Christian Brodbeck, Katerina Danae Kandylaki, O.E. Scharenborg
Learning to process speech in a foreign language involves learning new representations for mapping the auditory signal to linguistic structure. Behavioral experiments suggest that even listeners that are highly proficient in a non-native language experience interference from representations of their native language. However, much of the evidence for such interference comes from tasks that may inadvertently increase the salience of native language competitors. Here we tested for neural evidence of proficiency and native language interference in a naturalistic story listening task. We studied electroencephalography responses of 39 native speakers of Dutch (14 male) to an English short story, spoken by a native speaker of either American English or Dutch. We modeled brain responses with multivariate temporal response functions, using acoustic and language models. We found evidence for activation of Dutch language statistics when listening to English, but only when it was spoken with a Dutch accent. This suggests that a naturalistic, monolingual setting decreases the interference from native language representations, whereas an accent in the listeners’ own native language may increase native language interference, by increasing the salience of the native language and activating native language phonetic and lexical representations. Brain responses suggest that such interference stems from words from the native language competing with the foreign language in a single word recognition system, rather than being activated in a parallel lexicon. We further found that secondary acoustic representations of speech (after 200 ms latency) decreased with increasing proficiency. This may reflect improved acoustic-phonetic models in more proficient listeners. ...
Conference paper (2023) - Zhaofeng Lin, Tanvina Patel, Odette Scharenborg
Whispering is a distinct form of speech known for its soft, breathy, and hushed characteristics, often used for private communication. The acoustic characteristics of whispered speech differ substantially from normally phonated speech and the scarcity of adequate training data leads to low automatic speech recognition (ASR) performance. To address the data scarcity issue, we use a signal processing-based technique that transforms the spectral characteristics of normal speech to those of pseudo-whispered speech. We augment an End-to-End ASR with pseudo-whispered speech and achieve an 18.2 % relative reduction in word error rate for whispered speech compared to the baseline. Results for the individual speaker groups in the wTIMIT database show the best results for US English. Further investigation showed that the lack of glottal information in whispered speech has the largest impact on whispered speech ASR performance. ...
Conference paper (2023) - Bo Dekker, Alfred Schouten, Odette Scharenborg
Silent speech interfaces could enable people who lost the ability to use their voice or gestures to communicate with the external world, e.g., through decoding the person’s brain signals when imagining speech. Only a few and small databases exist that allow for the development and training of brain computer interfaces (BCIs) that can decode imagined speech from recorded brain signals. Here, we present an open database consisting of electroencephalography (EEG) and speech data from 20 participants recorded during the covert (imagined) and actual articulation of 15 Dutch prompts. A validation speaker-independent classification experiment using a ResNet-50 model with spatial-spectral-temporal features extracted from the EEG signals obtained an average accuracy of 70.6% for the classification of rest vs. covert vs. articulated speech trials. This and observed structural differences in the EEG signals between covert and articulated speech demonstrate that the EEG signals in the three classes contain discriminative information. ...
Conference paper (2023) - Zhe Wang, Shilong Wu, Diyuan Liu, More authors..., Hang Chen, Mao-Kui He, Jun Du, Chin-Hui Lee, Jingdong Chen, Shinji Watanabe, Sabato Marco Siniscalchi, Odette Scharenborg
The Multi-modal Information based Speech Processing (MISP) challenge aims to extend the application of signal processing technology in specific scenarios by promoting the research into wake-up words, speaker diarization, speech recognition, and other technologies. The MISP2022 challenge has two tracks: 1) audio-visual speaker diarization (AVSD), aiming to solve "who spoken when" using both audio and visual data; 2) a novel audio-visual diarization and recognition (AVDR) task that focuses on addressing "who spoken what when" with audio-visual speaker diarization results. Both tracks focus on the Chinese language, and use far-field audio and video in real home-tv scenarios: 2-6 people communicating each other with TV noise in the background. This paper introduces the dataset, track settings, and baselines of the MISP2022 challenge. Our analyses of experiments and examples indicate the good performance of AVDR baseline system, and the potential difficulties in this challenge due to, e.g., the far-field video quality, the presence of TV noise in the background, and the indistinguishable speakers. ...