Application of a registration method on magnetic resonance images to evaluate the displacement field of a human subject ear canal due to various earplug insertions

• Published in: The Journal of the Acoustical Society of America Vol. 143; no. 3; p. 1911
• Main Authors: Benacchio, Simon, Doutres, Olivier, Varoquaux, Arthur, Wagnac, Eric, Le Troter, Arnaud, Callot, Virginie, Sgard, Franck C.
• Format: Journal Article
• Language: English
• Published: 01.03.2018
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.5036224

Earplugs are a usual way to protect workers subjected to noise exposure. However, the efficiency of these hearing protection devices is often affected by induced discomforts. A factor suspected to impact both acoustical and physiological comfort attributes of earplugs is the deformation they apply on the ear canal walls. As the geometry of both open and occluded ear canal is difficult to obtain, the ear canal deformation due to earplug insertion is not trivial to evaluate. Current medical imaging techniques and image post-processing methods are promising tools to investigate this deformation. In a previous study of the authors, an approach using registration methods on medical images had been proposed to estimate the ear canal displacement field induced by earplug insertion. This approach had been validated in the case of computed tomography scans of a human-like artificial ear occluded by a controlled-shape custom molded earplug. In the present study, this approach is used to evaluate the ear canal displacement of a human subject for various earplug insertions (foam, pre-molded and custom made) in the case of magnetic resonance images. The computed displacement field shows noteworthy differences between each earplug and gives information on how and where the occluded ear canal deforms.