Industrial noise can be responsible for hearing loss for employees working in workshops. These losses can be recognized as professional deafness. In order to better control the noise levels in industrial rooms, it is necessary to focus on the interaction between the sound field and the walls of the room, which can have a regular or irregular relief. In this work, we are interested in walls that contain geometric irregularities and we focus in particular on the prediction of the sound pressure field diffused by rectangular parallelepiped shapes. A theoretical model has been developed for this purpose. It consists of superimposing the different sound fields diffracted by the thin rigid rectangular plates which constitute the parallelepiped shape. To do this, a combination of the sources image method and the theoretical Kobayashi Potential model (KP) has been implemented. The theoretical model is compared with the results of the numerical simulation and with the experimental results obtained in the INRS semi-anechoic room. Different geometric configurations are studied by changing the sizes and the spacing between the volumes. Thus, our model has been well validated on elementary networks for a wide frequency band.

Due to the increasing number of aided hearing impaired people, problems of their access to employment and stability of employment have become priority today. Once integrated into working life, hearing impaired people encounter difficulties in accessing information, communicating with colleagues and the hierarchy, and security problems. Deafness can jeopardize the effective performance of tasks and the safety of the worker because it causes difficulties in perceiving sound signals, understanding speech in the presence of noise and locating the source of sounds in space.

Hearing impaired people with hearing aids still face the problem of intelligibility, audibility, and protection against noise. However, favoring the wearing of hearing aids surely remains a solution because there are treatment options implemented in hearing aids that improve intelligibility and audibility. The objective is not to isolate the patient from his sound environment by allowing him to communicate with other employees and to perceive danger warning signals.

This study aims to propose acoustic solutions and recommendations for the room combined with proposals for existing hearing aid treatment options in order to keep these people in their professional activity. More specifically, the purpose is to study the improvement or deterioration of the audibility and/or the intelligibility brought by the hearing aids for hearing impaired people in their professional acoustic environment. The hearing protection of these people through their hearing aids is studied jointly.

For this, there are acoustic indicators representative of intelligibility and audibility such as the clarity index, the Speech Intelligibility Index, the spatialization and lateralization index, the interaural correlation coefficient, etc. We study the variation of these indices at the binaural listening point for aided hearing impaired people, placed at the work station, depending on the acoustic conditions (reverberant industrial rooms, fitted offices, …) and signal processing options available in hearing aids. These indicators can be determined by simulation of the spatial impulse responses which characterize in a simple way the room, the work place.

Listening in noise being the major complaint of aided hearing impaired people, hearing aid manufacturers have in recent decades developed and perfected signal processing options such as microphone directivity or noise reduction. The objective of this study is to investigate the effectiveness of these options on speech intelligibility using the Signal to Noise Ratio (SNR) indicator, for different types of masking noise, different manufacturers of hearing aids and different sound levels. The hearing simulation platform is used to reproduce the conditions of vocal audiometry in free field in noise and to access the sound signals at the output of hearing aids placed on the ears of the artificial head. Hearing aid output SNR is estimated using the method of Hagerman and Olofsson (2004) based on the diffusion of noise in phase opposition to separate speech from noise, here used within its validity limits. SNR values as a function of the frequency for the different noises tested make it possible to discuss the constraints and algorithmic strategies of the manufacturers. Finally, listening to the analyzed signals makes it possible to compare the quantified values ​​from our subjective point of view in terms of intelligibility and listening comfort.

The study consists in developing a mechanical model by FEM of the different structures of the whole ear: the aim is to simulate the propagation of a wave received at the entrance of the ear canal up to the cochlea.

External ear: the pavilion, the ear canal and the eardrum,

Middle ear: the ossicles and the cavity of the middle ear,

Inner ear: the cochlea.

This modeling makes it possible to optimize the fitting of a hearing aid and more particularly its earpiece in the external canal in order to improve the acoustic comfort for the patient with hearing aid: location relative to the eardrum and radiation mode of the earpiece.

This modeling will also make it possible to assess the effectiveness of individual noise protectors (PICB). The results thus obtained by modeling can be compared with the manufacturers’ technical sheets.

Many people are exposed to noise that can be continuous or short-lived (impulse noise). The latter may have a very high level and sudden (transient) variations in acoustic pressure. These two characteristics can cause more or less repairable intra-auditory effects (perforation of the eardrum, irreversible degradation of the hair cells). There are several forms and origins of impulse noise (detonation of a firearm, acoustic shock, deflagration, etc.). The objective of this study is to assess the harmful effect of this type of noise on the hearing system, bare ears or equipped with hearing aids, depending on the form and level of the impulse noise. An experimental device composed of an artificial head and a system for generating impulse noise by bursting membranes under pressure was set up in order to acquire the impulse signal perceived by the hearing system. It is thus possible to study the effectiveness of the impulse noise reducers implemented in hearing aids and ultimately, the destructive impact on the hair cells.