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FEATURED ARTICLE
Middle Ear Biomechanics: Smooth Sailing
Sunil Puria
Introduction
The ability to hear is vital and profound, enabling spoken communication and the emotional power of music, among many other experiences. Two ears allow us to localize sounds, alerting us to potential dangers both day and night. Furthermore, the production and perception of sound requires little energy.
Sound is diffracted by the external part of the ear, the pinna, then passes through the ear canal and vibrates the middle ear (Figure 1; see Multimedia1 at acousticstoday.org/puriamm). Although the sensing itself occurs inside the snail-shaped cochlea of the inner ear deep within the skull, the middle
ear is tasked with efficiently transmitting sound from the low-density, highly compressible air in the ear canal to the high-density nearly incompressible fluid in the cochlea (Brownell, 2017). Vibrations of the middle ear apparatus are necessary for sensitive hearing, so damage due to trauma or progressive disease processes, which can often be treated through surgery, reduces the effi- ciency and frequency range of the middle ear.
The Passage of Sound
From far away, the passage of sound through a healthy middle ear appears straightforward and unsurprising; it happens so faithfully and efficiently under normal
Figure 1. Anatomy of the human middle ear as reconstructed from micro computed tomography imaging. Key structures are labeled, except for suspensory ligaments that are shown in gray. For context, the anterior view shows the interconnection between the pinna, ear canal, middle ear, and cochlea. A three-dimensional representation of the middle ear that can be rotated and examined can be found at Multimedia1 at acousticstoday.org/puriamm. Figure was generated by Andrew Tubelli of the OtoBiomechanics Group at the Eaton-Peabody Laboratories (EPL).
©2020 Acoustical Society of America. All rights reserved.
https://doi.org/10.1121/AT.2020.16.3.27
Volume 16, issue 3 | Fall 2020 • Acoustics Today 27