arXiv subjects

Volker Hohmann

Publications and source records attributed to Volker Hohmann.

17 recordsLinked to original sources

arXiv2026

The Virtual Hearing Clinic (VHC)- a modular online platform for hearing research and hearing health care

Objective: The aim is to introduce the concept of the Virtual Hearing Clinic (VHC), give an overview of the current status and exemplify its feasibility with data from a diagnostics module obtaining hearing thresholds. Design: The architecture of the VHC is described and an overview of functional modules that have been developed and tested in respective studies is given. As a functional example data from an experiment is presented. Hearing thresholds were obtained from 20 subjects with hearing loss with the VHC using the Graded Response Bracketing (GraBr) procedure and compared to reference thresholds obtained with a clinical audiometer. Results: Median VHC-based hearing thresholds over all frequencies did not differ significantly from the reference with values of 57.4 dB SPL (VHC) and 55.5 dB SPL (reference). The shape of the frequency-dependent thresholds was also found to be very similar for 250 Hz to 4 kHz. Results for 6 kHz showed larger differences. Conclusion: The VHC is suitable as a mobile hearing health application and to collect data for audiological research. By offering flexibility in time and location it can lower barriers for hearing health care and enable collecting large datasets that are needed for the advancement of data-driven audiology.

physics.med-ph↗

arXiv2025

Effect of Avatar Head Movement on Communication Behaviour, Experience of Presence and Conversation Success in Triadic Conversations

Interactive communication in virtual reality can be used in experimental paradigms to increase the ecological validity of hearing device evaluations. This requires the virtual environment to elicit natural communication behaviour in listeners. This study evaluates the effect of virtual animated characters' head movements on participants' communication behaviour and experience. Triadic conversations were conducted between a test participant and two confederates. To facilitate the manipulation of head movements, the conversation was conducted in telepresence using a system that transmitted audio, head movement data and video with low delay. The confederates were represented by virtual animated characters (avatars) with different levels of animation: Static heads, automated head movement animations based on speech level onsets, and animated head movements based on the transmitted head movements of the interlocutors. A condition was also included in which the videos of the interlocutors' heads were embedded in the visual scene. The results show significant effects of animation level on the participants' speech and head movement behaviour as recorded by physical sensors, as well as on the subjective sense of presence and the success of the conversation. The largest effects were found for the range of head orientation during speech and the perceived realism of avatars. Participants reported that they were spoken to in a more helpful way when the avatars showed head movements transmitted from the interlocutors than when the avatars' heads were static. We therefore conclude that the representation of interlocutors must include sufficiently realistic head movements in order to elicit natural communication behaviour.

cs.HC↗

arXiv2025

Neural Speech Tracking in a Virtual Acoustic Environment: Audio-Visual Benefit for Unscripted Continuous Speech

The audio visual benefit in speech perception, where congruent visual input enhances auditory processing, is well documented across age groups, particularly in challenging listening conditions and among individuals with varying hearing abilities. However, most studies rely on highly controlled laboratory environments with scripted stimuli. Here, we examine the audio visual benefit using unscripted, natural speech from untrained speakers within a virtual acoustic environment. Using electroencephalography (EEG) and cortical speech tracking, we assessed neural responses across audio visual, audio only, visual only, and masked lip conditions to isolate the role of lip movements. Additionally, we analysed individual differences in acoustic and visual features of the speakers, including pitch, jitter, and lip openness, to explore their influence on the audio visual speech tracking benefit. Results showed a significant audio visual enhancement in speech tracking with background noise, with the masked lip condition performing similarly to the audio-only condition, emphasizing the importance of lip movements in adverse listening situations. Our findings reveal the feasibility of cortical speech tracking with naturalistic stimuli and underscore the impact of individual speaker characteristics on audio-visual integration in real world listening contexts.

eess.AS↗

arXiv2023

Video Screens for Hearing Research: Transmittance and Reflectance of Professional and Other Fabrics

Virtual reality labs for hearing research are commonly designed to achieve maximal acoustical accuracy of virtual environments. For a high immersion, 3D video systems are applied, that ideally do not influence the acoustical conditions. In labs with projection systems, the video screens have a potentially strong influence depending on their size, their acoustical transmittance and their acoustical reflectance. In this study, the acoustical transmittance and reflectance of six professional acoustic screen fabrics and 13 general purpose fabrics were measured considering two tension conditions. Additionally, the influence of a black backing was tested, which is needed to reduce the optical transparency of fabrics. The measured transmission losses range from -5 dB to -0.1 dB and the reflected sound pressure levels from -32 dB to -4 dB. The best acoustical properties were measured for a chiffon fabric.

physics.med-ph↗

arXiv2023

The future of hearing aid technology

Background. Hearing aid technology has proven successful in the rehabilitation of hearing loss, but its performance is still limited in difficult everyday conditions characterized by noise and reverberation. Objectives. Introduction to the current state of hearing aid technology and presentation of the current state of research and future development. Methods. Current literature is analyzed and several specific new developments are presented. Results. Both objective and subjective data from empirical studies show the limitation of current technology. Examples of current research show the potential of machine-learning based algorithms and multi-modal signal processing for improving speech processing and perception, of using virtual reality for improving hearing device fitting and of mobile health technology for improving hearing-health services. Conclusions. Hearing device technology will remain a key factor in the rehabilitation of hearing impairment. New technology such as machine learning, and multi-modal signal processing, virtual reality and mobile health technology will improve speech enhancement, individual fitting and communication training.

eess.AS↗

arXiv2023

Comparison of a Head-Mounted Display and a Curved Screen in a Multi-Talker Audiovisual Listening Task

Introduction: Virtual audiovisual technology and its methodology has yet to be established for psychoacoustic research. This study examined the effects of different audiovisual conditions on preference when listening to multi-talker conversations. The study's goal is to explore and assess audiovisual technologies in the context of hearing research. Methods: The participants listened to audiovisual conversations between four talkers. Two displays were tested and compared: a curved screen (CS) and a head-mounted display (HMD). Using three visual conditions (audio-only, virtual characters and video recordings), three groups of participants were tested: seventeen young normal-hearing, ten older normal-hearing, and ten older hearing-impaired listeners. Results: Open interviews showed that the CS was preferred over the HMD for older normal-hearing participants and that video recordings were the preferred visual condition. Young and older hearing-impaired participants did not show a preference between the CS and the HMD. Conclusions: CSs and video recordings should be the preferred audiovisual setup of laboratories and clinics, although HMDs and virtual characters can be used for hearing research when necessary and suitable.

cs.HC↗

arXiv2022

Vehicle Noise: Comparison of Loudness Ratings in the Field and the Laboratory

Objective: Distorted loudness perception is one of the main complaints of hearing aid users. Being able to measure loudness perception correctly in the clinic is essential for fitting hearing aids. For this, experiments in the clinic should be able to reflect and capture loudness perception as in everyday-life situations. Little research has been done comparing loudness perception in the field and in the laboratory. Design: Participants rated the loudness in the field and in the laboratory of 36 driving actions done by four different vehicles. The field measurements were done in a restricted street and recorded with a 360deg camera and a tetrahedral microphone. The recorded stimuli, which are openly accessible, were presented in three different conditions in the laboratory: 360deg video recordings with a head-mounted display, video recordings with a desktop monitor, and audio-only. Sample: Thirteen normal-hearing participants and 18 hearing-impaired participants participated in the study. Results: The driving actions were rated significantly louder in the laboratory than in the field for the audio-only condition. These loudness rating differences were bigger for louder sounds in two laboratory conditions, i.e., the higher the sound level of a driving action was the more likely it was to be rated louder in the laboratory. There were no significant differences in the loudness ratings between the three laboratory conditions and between groups. Conclusions: The results of this experiment further remark the importance of increasing the realism and immersion when measuring loudness in the clinic.

q-bio.NC↗

arXiv2022

Open community platform for hearing aid algorithm research: open Master Hearing Aid (openMHA)

open Master Hearing Aid (openMHA) was developed and provided to the hearing aid research community as an open-source software platform with the aim to support sustainable and reproducible research towards improvement and new types of assistive hearing systems not limited by proprietary software. The software offers a flexible framework that allows the users to conduct hearing aid research using tools and a number of signal processing plugins provided with the software as well as the implementation of own methods. The openMHA software is independent of a specific hardware and supports Linux, macOS and Windows operating systems as well as 32-bit and 64-bit ARM-based architectures such as used in small portable integrated systems. www.openmha.org

eess.AS↗

arXiv2021

The Period-Modulated Harmonic Locked Loop (PM-HLL): A low-effort algorithm for rapid time-domain multi-periodicity estimation

Many speech and music analysis and processing schemes rely on an estimate of the fundamental frequency $f_0$ of periodic signal components. Most established schemes apply rather unspecific signal models such as sinusoidal models to the estimation problem, which may limit time resolution and estimation accuracy. This study proposes a novel time-domain locked-loop algorithm with low computational effort and low memory footprint for $f_0$ estimation. The loop control signal is directly derived from the input time signal, using a harmonic signal model. Theoretically, this allows for a noise-robust and rapid $f_0$ estimation for periodic signals of arbitrary waveform, and without the requirement of a prior frequency analysis. Several simulations with short signals employing different types of periodicity and with added wide-band noise were performed to demonstrate and evaluate the basic properties of the proposed algorithm. Depending on the Signal-to-Noise Ratio (SNR), the estimator was found to converge within 3-4 signal repetitions, even at SNR close to or below 0dB. Furthermore, it was found to follow fundamental frequency sweeps with a delay of less than one period and to track all tones of a three-tone musical chord signal simultaneously. Quasi-periodic sounds with shifted harmonics as well as signals with stochastic periodicity were robustly tracked. Mean and standard deviation of the estimation error, i.e., the difference between true and estimated $f_0$, were at or below 1 Hz in most cases. The results suggest that the proposed algorithm may be applicable to low-delay speech and music analysis and processing.

cs.SD↗

arXiv2021

The Concurrent OLSA test: A method for speech recognition in multi-talker situations at fixed SNR

A multi-talker paradigm is introduced that uses different attentional processes to adjust speech recognition scores with the goal to conduct measurements at high signal-to-noise ratios. The basic idea is to simulate a group conversation with three talkers and a participant. Talkers alternately speak sentences of the German matrix test OLSA. Each time a sentence begins with the name "Kerstin" (call sign), the participant is addressed and instructed to repeat the last words of all sentences from that talker, until another talker begins a sentence with "Kerstin". The alternation of the talkers is implemented with an adjustable overlap time that causes an overlap between the call sign "Kerstin" and the target words to be repeated. Thus, the two tasks of detecting "Kerstin" and repeating target words are to be processed at the same time as a dual task. The paradigm was tested with 22 young normal-hearing participants for three overlap times (0.6 s, 0.8 s, 1.0 s). Results for these overlap times show significant differences with median target word recognition scores of 88%, 82%, and 77%, respectively (including call sign and dual task effects). A comparison of the dual task with the corresponding single tasks suggests that the observed effects reflect an increased cognitive load.

physics.med-ph↗

arXiv2021

Development and Evaluation of Video Recordings for the OLSA Matrix Sentence Test

One of the established multi-lingual methods for testing speech intelligibility is the matrix sentence test (MST). Most versions of this test are designed with audio-only stimuli. Nevertheless, visual cues play an important role in speech intelligibility, mostly making it easier to understand speech by speechreading. In this work we present the creation and evaluation of dubbed videos for the Oldenburger female MST (OLSA). 28 normal-hearing participants completed test and retest sessions with conditions including audio and visual modalities, speech in quiet and noise, and open and closed-set response formats. The levels to reach 80% sentence intelligibility were measured adaptively for the different conditions. In quiet, the audiovisual benefit compared to audio-only was 7 dB in sound pressure level (SPL). In noise, the audiovisual benefit was 5 dB in signal-to-noise ratio (SNR). Speechreading scores ranged from 0% to 84% speech reception in visual-only sentences, with an average of 50% across participants. This large variability in speechreading abilities was reflected in the audiovisual speech reception thresholds (SRTs), which had a larger standard deviation than the audio-only SRTs. Training and learning effects in audiovisual sentences were found: participants improved their SRTs by approximately 3 dB SNR after 5 trials. Participants retained their best scores on a separate retest session and further improved their SRTs by approx. -1.5 dB.

eess.AS↗

arXiv2021

Interaction of hearing aids with self-motion and the influence of hearing impairment

When listening to a sound source in everyday-life situations, typical movement behavior can lead to a mismatch between the direction of the head and the direction of interest. This could reduce the performance of directional algorithms, as was shown in previous work for head movements of normal-hearing listeners. However, the movement behavior of hearing-impaired listeners and hearing aid users might be different, and if hearing aid users adapt their self-motion because of the directional algorithm, its performance might increase. In this work we therefore investigated the influence of hearing impairment on self-motion, and the interaction of hearing aids with self-motion. In order to do this, the self-motion of three hearing-impaired (HI) participant groups, aided with an adaptive differential microphone (ADM), aided without ADM, and unaided, was compared, also to previously measured self-motion data from younger and older normal-hearing (NH) participants. The self-motion was measured in virtual audiovisual environments (VEs) in the laboratory. Furthermore, the signal-to-noise ratios (SNRs) and SNR improvement of the ADM resulting from the head movements of the participants were estimated with acoustic simulations. A strong effect of hearing impairment on self-motion was found, which led to an overall increase in estimated SNR of 0.8 dB for the HI participants compared to the NH participants, and differences in estimated SNR improvement of the ADM. However, the self-motion of the HI participants aided with ADM and the other HI participants was very similar, indicating that they did not adapt their self-motion because of the ADM.

physics.med-ph↗

arXiv2018

Influence of visual cues on head and eye movements during listening tasks in multi-talker audiovisual environments with animated characters

Recent studies of hearing aid benefits indicate that head movement behavior influences performance. To systematically assess these effects, movement behavior must be measured in realistic communication conditions. For this, the use of virtual audiovisual environments with animated characters as visual stimuli has been proposed. It is unclear, however, how these animations influence the head- and eye-movement behavior of subjects. Here, two listening tasks were carried out with a group of 14 young normal hearing subjects to investigate the influence of visual cues on head- and eye-movement behavior; on combined localization and speech intelligibility task performance; as well as on perceived speech intelligibility, perceived listening effort and the general impression of the audiovisual environments. Animated characters with different lip-syncing and gaze patterns were compared to an audio-only condition and to a video of real persons. Results show that movement behavior, task performance, and perception were all influenced by visual cues. The movement behavior of young normal hearing listeners in animation conditions with lip-syncing was similar to that in the video condition. These results in young normal hearing listeners are a first step towards using the animated characters to assess the influence of head movement behavior on hearing aid performance.

physics.med-ph↗

arXiv2018

A toolbox for rendering virtual acoustic environments in the context of audiology

A toolbox for creation and rendering of dynamic virtual acoustic environments (TASCAR) that allows direct user interaction was developed for application in hearing aid research and audiology. This technical paper describes the general software structure and the time-domain simulation methods, i.e., transmission model, image source model, and render formats, used to produce virtual acoustic environments with moving objects. Implementation-specific properties are described, and the computational performance of the system was measured as a function of simulation complexity. Results show that on commercially available commonly used hardware the simulation of several hundred virtual sound sources is possible in the time domain.

cs.SD↗

arXiv2017

Combination of binaural and harmonic masking release effects in the detection of a single component in complex tones

Both harmonic and binaural signal properties are relevant for auditory processing. To investigate how these cues combine in the auditory system, detection thresholds for an 800-Hz tone masked by a diotic (i.e., identical between the ears) harmonic complex tone were measured in six normal-hearing subjects. The target tone was presented either diotically or with an interaural phase difference (IPD) of 180 degree and in either harmonic or "mistuned" relationship to the diotic masker. Three different maskers were used, a resolved and an unresolved complex tone (fundamental frequency: 160 and 40 Hz) with four components below and above the target frequency and a broadband unresolved complex tone with 12 additional components. The target IPD provided release from masking in most masker conditions, whereas mistuning led to a significant release from masking only in the diotic conditions with the resolved and the narrowband unresolved maskers. A significant effect of mistuning was neither found in the diotic condition with the wideband unresolved masker nor in any of the dichotic conditions. An auditory model with a single analysis frequency band and different binaural processing schemes was employed to predict the data of the unresolved masker conditions. Sensitivity to modulation cues was achieved by including an auditory-motivated modulation filter in the processing pathway. The predictions of the diotic data were in line with the experimental results and literature data in the narrowband condition, but not in the broadband condition, suggesting that across-frequency processing is involved in processing modulation information. The experimental and model results in the dichotic conditions show that the binaural processor cannot exploit modulation information in binaurally unmasked conditions.

cs.SD↗

arXiv2015

Evaluation of spatial audio reproduction schemes for application in hearing aid research

Loudspeaker-based spatial audio reproduction schemes are increasingly used for evaluating hearing aids in complex acoustic conditions. To further establish the feasibility of this approach, this study investigated the interaction between spatial resolution of different reproduction methods and technical and perceptual hearing aid performance measures using computer simulations. Three spatial audio reproduction methods -- discrete speakers, vector base amplitude panning and higher order ambisonics -- were compared in regular circular loudspeaker arrays with 4 to 72 channels. The influence of reproduction method and array size on performance measures of representative multi-microphone hearing aid algorithm classes with spatially distributed microphones and a representative single channel noise-reduction algorithm was analyzed. Algorithm classes differed in their way of analyzing and exploiting spatial properties of the sound field, requiring different accuracy of sound field reproduction. Performance measures included beam pattern analysis, signal-to-noise ratio analysis, perceptual localization prediction, and quality modeling. The results show performance differences and interaction effects between reproduction method and algorithm class that may be used for guidance when selecting the appropriate method and number of speakers for specific tasks in hearing aid research.

cs.SD↗

arXiv2015

Online Monaural Speech Enhancement Based on Periodicity Analysis and A Priori SNR Estimation

This paper describes an online algorithm for enhancing monaural noisy speech. Firstly, a novel phase-corrected low-delay gammatone filterbank is derived for signal subband decomposition and resynthesis; the subband signals are then analyzed frame by frame. Secondly, a novel feature named periodicity degree (PD) is proposed to be used for detecting and estimating the fundamental period (P0) in each frame and for estimating the signal-to-noise ratio (SNR) in each frame-subband signal unit. The PD is calculated in each unit as the multiplication of the normalized autocorrelation and the comb filter ratio, and shown to be robust in various low-SNR conditions. Thirdly, the noise energy level in each signal unit is estimated recursively based on the estimated SNR for units with high PD and based on the noisy signal energy level for units with low PD. Then the a priori SNR is estimated using a decision-directed approach with the estimated noise level. Finally, a revised Wiener gain is calculated, smoothed, and applied to each unit; the processed units are summed across subbands and frames to form the enhanced signal. The P0 detection accuracy of the algorithm was evaluated on two corpora and showed comparable performance on one corpus and better performance on the other corpus when compared to a recently published pitch detection algorithm. The speech enhancement effect of the algorithm was evaluated on one corpus with two objective criteria and showed better performance in one highly non-stationary noise and comparable performance in two other noises when compared to a state-of-the-art statistical-model based algorithm.

cs.SD↗