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Chapter 15 Audiology
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
Some of the anatomy and the physics of the sense of hearing were explained in Chapter 3 (section 3.4.4). In this section we will briefly review and expand on some aspects of these topics. The ear is a transducer which is connected to the brain via the eighth cranial nerve. Sound travels down the external ear canal and causes the eardrum (the tympanic membrane) to vibrate. The eardrum is oval in shape, has a maximum width of about 8 mm and is about 0.1 mm in thickness. The vibrations of the membrane, which have an amplitude approximately equal to one atomic radius (10-10 m) at sound intensities close to the threshold of hearing, cause the small bones within the middle ear to vibrate. These bones, or ossicles, transmit the vibrations to a membrane that covers the entrance to the fluid-filled inner ear. The ossicles appear to be pivoted in a manner which makes them insensitive to vibrations of the skull but able to magnify the forces applied to the eardrum, by a factor of about 1.6. The difference in area of the tympanic membrane and the window into the inner ear gives a much larger increase in transmitted pressure. These magnified changes in force and pressure act within the cochlea of the middle ear to transduce the vibratory energy into electrical energy. There is no widely accepted theory to explain how the cochlea generates the pattern of nerve impulses which we interpret as sound. Some of the possible mechanisms were described in Chapter 3.
Audition and Vestibular Function
Published in Nancy J. Stone, Chaparro Alex, Joseph R. Keebler, Barbara S. Chaparro, Daniel S. McConnell, Introduction to Human Factors, 2017
Nancy J. Stone, Chaparro Alex, Joseph R. Keebler, Barbara S. Chaparro, Daniel S. McConnell
Figure 4.3 depicts a schematic of the human ear. The major structural components of the ear can be organized into three regions: the outer, middle, and inner ear. The structure of the outer ear consists of the pinna (the external ear structure) and auditory canal that direct sound toward the tympanic membrane (ear drum) that vibrates back and forth in response to the changes in air pressure produced by a sound. The ear canal not only helps protect the ear drum but also has resonant properties that increase the SPL of frequencies in the range of 2000–5000 Hz by as much 12 dB. The movements of the tympanic membrane are conveyed to the inner ear by the ossicles of the middle ear. The ossicles are three bones called the malleus, incus, and stapes, which link the tympanic membrane and the oval window of the inner ear. Attached to the ossicles are two muscles called the tensor tympani and the stapedius that tighten in response to loud noises, thereby offering some protection from loud, extended sounds. However, this tightening of the muscles, called the aural reflex (Reger, 1960), is relatively slow (approximately 35–140 ms) and offers little protective benefit from loud impulsive sounds like that produced by a gun.
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Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[biomedical, general] Anatomical segment in the hearing mechanism for mammals conveying the longitudinal pressure wave incident on the eardrum (tympanic membrane) at the end of the outer ear, to the over window on the cochlea of the inner ear. The middle ear has a mechanism of controlling the loudness of the sound propagated to the inner ear (primarily to prevent structural damage as well as increase the amplitude and frequency resolution). The pivoted bone system (ossicles) in the middle ear consisting of the malleus (“hammer”), incus (“anvil”), and stapes (“stirrup”) that can be relaxed with respect to its interconnection, hence reducing the magnitude of translational movement; reducing the amplitude applied to the oval window. Keeping in mind that the tympanic membrane is 20 times larger in area than the oval window, this indicates the first mechanism of “amplification” available for hearing. The ossicles can respond to a displacement of the tympanic membrane in the order of nanometers, setting the lower limit of hearing at (approximately) 0 dB at approximately 3500 Hz for a healthy young human ear. With excessive loudness, the fibrous/muscular connections between the ossicles wear down, reducing the sensitivity, leading to gradual procession of deafness. Additionally age-related degeneration of the elasticity of biological materials hearing will decline in both frequency response and intensity sensitivity (see Figure M.106).
Design of a resilient ring for middle ear’s chamber stapes prosthesis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Emilia Anna Kiryk, Konrad Kamieniecki, Monika Kwacz
Stapes prostheses are used for surgical treatment of otosclerosis, which is an illness affecting auditory ossicles located in the middle ear. The ossicles (malleus, incus and stapes) link the outer and inner ear and transmit sound vibrations from the tympanic membrane to the oval window (OW). The stapes footplate (SF) is suspended on a highly elastic annular ligament (AL) in the OW niche. The AL enables the stapes to vibrate and to generate a pressure wave in the perilymph fluid. Otosclerosis immobilizes the stapes due to stiffening of the AL. This leads to a decrease in stimulation of the perilymph and manifests by conductive hearing loss (CHL). Otosclerosis is the cause of almost 22% of all CHL (Potocka et al. 2010).
Semi-automatic 3D reconstruction of middle and inner ear structures using CBCT
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2023
Florian Beguet, Thierry Cresson, Mathieu Schmittbuhl, Cédric Doucet, David Camirand, Philippe Harris, Jean-Luc Mari, Jacques de Guise
The middle ear is a space filled with air located in the temporal bone between the outer ear and the inner ear. It contains a chain consisting of three movable ossicles: the malleus, the incus (Figure 1b) and the stapes (Figure 1c). The vibrations of the air captured by the eardrum are amplified along the ossicular chain and then transmitted to the inner ear via the oval window. The ossicles are eminently complex structures especially the stapes where a list of 14 probative measures has been determined (Farahani and Nooranipour 2008). In addition, each of these structures can be the cause of many hearing problems (Nager 1993).