Author(s): Sgard Franck, Benacchio Simon, Luan Yu, Xu Huiyang, Carillo Kevin, Doutres Olivier, Nelisse Hugues, Wagnac Eric , De Guise Jacques
One of the reasons why hearing protectors are not fully efficient at protecting against noisy environments is the acoustical discomfort they induce. This discomfort may incite an individual to wear his protector incorrectly or to remove it, thereby reducing its performance. The acoustical discomfort depends on the acoustic pressure value at the eardrum of the protected ear. To reduce it efficiently, a tool for the acoustical design of the hearing protector device (HPD) allowing for determining this acoustic pressure, may prove to be useful. This paper presents the methodology to develop a unique and realistic numerical Vibroacoustic Model (VM) in the audible frequency range of a human head wearing an HPD together with an associated instrumented Experimental Anatomical Phantom (EAP). The VM consists of a 3D finite element model of the head of a living subject wearing an HPD reconstructed from medical images. This model will be validated and calibrated step by step against an EAP made up of synthetic materials with average mechanical properties. It will then be calibrated against the human subject from which the VM is the replica. A new EAP will be fabricated based on the updated mechanical properties of the calibrated VM. Finally, it will be exploited to study a variety of earplugs and earmuffs together with the sound transmission mechanisms through the head/HPD system. Preliminary results on some stages of the VM development are also presented. A registration method applied on medical images of a simplified EAP of the external ear without and with earplugs show to which extent the latter can deform the ear canal. The deformed shape of earplugs can also be identified. Comparisons between the predicted sound attenuation of a commercial earmuff and experimental data in a simplified configuration are presented to evaluate an improved earmuff finite element model.
Name: Dr Franck Sgard