Audioprothèse | EPFL Graph Search

L'audioprothèse, appelée familièrement « appareil auditif », a remplacé le sonotone à entonnoir, elle a pour objectif de compenser une perte auditive par un appareillage adéquat, et de pouvoir selon les cas pallier les désordres donnés par la "surdité" dans la capacité d'orientation de la personne, la position du corps dans l'espace et sa trajectoire obtenue. L'appareillage auditif comprend : le choix, l'adaptation, la délivrance, le contrôle d'efficacité immédiate et permanente de la prothèse auditive et l'éducation prothétique du déficient de l'ouïe appareillé. Pour le soutien de l'audition, la prothèse auditive peut être externe. Dans certains cas de surdité plus profonde, si cela est possible et que les conséquences de l'intervention acceptables, on peut disposer d'un dispositif implantable :

prothèse auditive à ancrage osseux (en Bone Anchored Hearing Aid, BAHA) pour des cas de surdités dites de transmission ou pour des patients souffrant d'otites chroniques. Cette prot

Active Control mitigating the Ear Canal Occlusion Effect caused by Hearing Aids

Thomas Stefan Zurbrügg

The World Health Organization (WHO) estimates the prevalence of a disabling hearing loss to be above 5% world-wide 1. A treatment with a hearing aid - be it behind-the-ear (BTE), in-the-ear (ITE) or receiver-in-canal (RIC) - involves some degree of occlusion of the external ear canal. In many cases, this so-called occlusion effect (OE) leads to an unfamiliar perception of the hearing aid user’s own voice. This fact represents a limiting factor regarding the acceptance of hearing aids by potential users. This thesis focuses on modeling the physical occlusion effect caused by hearing aids and the investigation of active control approaches mitigating this adverse effect. A simple model based on audiological transfer functions is presented, discussed and validated in the first part of the thesis. This model is subsequently used as a basis for the analysis and the synthesis of an active control approach based on sound pressure feedback. The objective and subjective validation of this approach implemented as a prototype setup in a user-study is presented. Finally, the use of the insights from the first part for fitting a hearing aid incorporating such active occlusion control is suggested.

EPFL2014

Auditory externalization of a remote microphone signal

Vincent Pierre Olivier Grimaldi

A remote microphone (RM) system can be used in combination with wearable binaural communication devices, such as hearing aids (HAs), to improve speech intelligibility. Typically, a speaker is equipped with a body-worn microphone which enables to pick up their voice with a high signal-to-noise ratio (SNR). However, if this signal is played diotically through the receivers (i.e. the same signal in both ears), the necessary cues enabling the auditory system to locate the sound source are bypassed. This can affect the ability of the listener to feel immersed in the environment or to follow a conversation, especially for hearing-impaired (HI) listeners. Auditory sound source localization in humans is performed by the auditory system owing to the interpretation of various cues related to the physical sound propagation from this source to the eardrums of the listener. This is mainly enabled by the binaural structure of the auditory system.Previous works have successfully developed a method to provide a simplified spatialization of the RM signal which enabled normal-hearing (NH) and HI listeners to locate sound sources in azimuth, while preserving speech intelligibility. However, the proposed method yielded common spatial hearing perceptual artefacts, such as in-head localization and front/back confusion.This thesis is devoted to the investigation and the perceptual evaluation of wearable devices-compatible audio playback solutions aiming at enhancing the realism of this spatialization. In particular, the goal is to improve the externalization of a sound source, i.e. to ensure it is perceived outside the head, and possibly at a certain distance corresponding to its physical location in the environment. For this purpose, early reflections (ERs) in a room play a key role. Hence, several signal processing approaches to provide ERs in the binaural synthesis were investigated. Subsequently, a subjective listening study was conducted, in which NH and HI aided listeners had to evaluate the perceived auditory distance with various binaural rendering strategies. The results show that the superimposition of ERs with the considered methods significantly improves the perception of auditory distance for NH and HI listeners. The study also provides insights about auditory distance perception in aided HI listeners with severe-to-profound hearing loss. A follow-up study was conducted with NH listeners and showed that a complete implementation of these strategies might improve auditory distance perception while preserving spatial awareness. In these studies, subjects had their head fixed.Previous studies have shown that head movements coupled with head-tracking can contribute to the auditory externalization of a virtual sound source. The next part of this thesis reports the development of a head-tracking algorithm compatible with wearable devices, relying solely on two 3-axis accelerometers. While showing promising results, the limitations of the developed algorithm still yield mismatches in the estimation. Consequently, a subjective listening test was conducted with NH listeners to study the effect of head-tracking artefacts on the perception of externalization and the performance in azimuth localization of a sound source. The results suggest that auditory externalization is not affected by a large latency or the amplitude mismatch. Latency did not decrease the performance in localization either, contrarily to the amplitude mismatch.

EPFL2022

Spatial hearing rendering in wireless microphone systems for binaural hearing aids

Gilles André Courtois

In 2015, 360 million people, including 32 million children, were suffering from hearing impairment all over the world. This makes hearing disability a major worldwide issue. In the US, the prevalence of hearing loss increased by 160% over the past generations. However, 72% of the 34 million impaired American persons (11% of the population) still have an untreated hearing loss. Among the various current solutions alleviating hearing disability, hearing aid is the only non-invasive and the most widespread medical apparatus. Combined with hearing aids, assisting listening devices are a powerful answer to address the degraded speech understanding observed in hearing-impaired subjects, especially in noisy and reverberant environments. Unfortunately, the conventional devices do not accurately render the spatial hearing property of the human auditory system, weakening their benefits. Spatial hearing is an attribute of the auditory system relying on binaural hearing. With 2 ears, human beings are able to localize sounds in space, to get information about the acoustic surroundings, to feel immersed in environments... Furthermore, it strongly contributes to speech intelligibility. It is hypothesized that recreating an artificial spatial perception through the hearing aids of impaired people might allow for recovering a part of these subjects' hearing performance. This thesis investigates and supports the aforementioned hypothesis with both technological and clinical approaches. It reveals how certain well-established signal processing methods can be integrated in some assisting listening devices. These techniques are related to sound localization and spatialization. Taking into consideration the technical constraints of current hearing aids, as well as the characteristics of the impaired auditory system, the thesis proposes a novel solution to restore a spatial perception for users of certain types of assisting listening devices. The achieved results demonstrate the feasibility and the possible implementation of such a functionality on conventional systems. Additionally, this thesis examines the relevance and the efficiency of the proposed spatialization feature towards the enhancement of speech perception. Via a clinical trial involving a large number of patients, the artificial spatial hearing shows to be well appreciated by disabled persons, while improving or preserving their current hearing abilities. This can be considered as a prominent contribution to the current scientific and technological knowledge in the domain of hearing impairment.