Hearing loss | EPFL Graph Search

Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken language, and in adults it can create difficulties with social interaction and at work. Hearing loss can be temporary or permanent. Hearing loss related to age usually affects both ears and is due to cochlear hair cell loss. In some people, particularly older people, hearing loss can result in loneliness. Deaf people usually have little to no hearing. Hearing loss may be caused by a number of factors, including: genetics, ageing, exposure to noise, some infections, birth complications, trauma to the ear, and certain medications or toxins. A common condition that results in hearing loss is chronic ear infections. Certain infections during pregnancy, such

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.

EPFL2016

Conformable neural interfaces : from engineering stretchability at the micro-scale to translational applications

Florent-Valéry Coen

Recently, flexible and soft bioelectronic interfaces have been proposed as a solution to improve existing neural interfaces that currently present mechanical mismatch with the soft tissue. These are devices fabricated with thin polymeric or elastomeric backbones to enable an optimal contact to the target tissue as well as reduced mechanical mismatch. For this the electrical interconnects that carry the electrical information from the tissue or deliver the stimulation charges need to be elastic to accommodate the stresses and remain conductive. Several strategies for creating stretchable tracks have been proposed in the past but are not compatible with high-density low-profile electrode arrays for chronic implantation in vivo.A method of patterning thin material stacks of flexible polymers and platinum layers embedded in silicone membranes was proposed in the Laboratory for Soft Bioelectronic Interfaces at EPFL. By creating specific microscopic cuts in the materials permits the out-of-plane deformation of the film and enables stretchability above 50% strain while remaining conductive. However, the previous fabrication method was not optimal, was not hermetically encapsulated and not reliable. In this thesis, novel soft electrode arrays were designed and fabricated using an improved manufacturing process named core-shell micropatterning. This enables fully encapsulated electrical tracks that can be micropatterned with superior electromechanical performances and notable increase in hermetic barrier lifetimes. Additionally, this method was applied to other material systems enabling new functions such as completely transparent devices to enable concurrent optical stimulation and microscopy through the implanted electrodes.These fabricated devices were applied to several device concepts in multiple animal models. First, microelectrode arrays for electrocorticography (ECoG) recordings were designed to be implanted over the auditory cortex of rat and non-human primate (NHP) models to capture evoked potentials from acoustic stimulation. This enabled the precise tonotopic mapping and the spatial representation of the auditory cortex. Next, auditory brainstem implants (ABI), targeting the cochlear nucleus (CN) after the auditory nerve were designed. This implant needs to conform to the curved surface of the CN and stimulate the auditory pathway. In non-human primates, the placement of this device is challenging and new tools were developed for the insertion of the device. Finally, the combination of soft ABI and ECoG was implanted in chronic settings in a NHP to evoke auditory percepts from brainstem stimulation that could be monitored using the cortical evoked potentials. This will enable the fine-tuning of stimulation protocols for hearing restoration and verify the stability of the implants over time.Overall, this work represents a framework to design and fabricate soft electrode arrays that can be applied for recording and stimulation in small to large animal models in a reliable way. The careful design of the system around the implant such as fine-tuning of microfabrication parameters, the characterization in vitro, device geometry, connection scheme, experimental setup and tracking of the device properties in vivo enables reliable long-term implantations in new experimental paradigms.

EPFL2022

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