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Acoustic Criteria
Published in Randall F. Barron, Industrial Noise Control and Acoustics, 2002
The main part of the inner ear is the cochlea, which is a bony tube about 34 mm (1.34 in) long, filled with liquid and coiled like a snail’s shell. The cochlea makes about 234 turns around a central hollow passage that contains the nerve fibers going to the brain. The cochlea is illustrated in Fig. 6-2. There is a bony projection or shelf and a membrane called the basilar membrane that runs the length of the cochlea. The basilar membrane divides the cochlea into two chambers, the upper chamber or scala vestibuli, and the lower chamber or scala tympani. There is a small opening at the end of the cochlea, called the helicotrema, which provides a connecting passage between the upper and lower chambers. The basilar membrane varies in width from 0.2 mm (0.008 in) at the oval window to about 0.5 mm (0.020 in) at the end of the cochlea chamber.
Basic principles
Published in Michael Talbot-Smith, Audio Engineer's Reference Book, 2013
John Ratcliff, Talbot-Smith Michael, J. Patrick Wilson, Louis D. Fielder, Glynne Parry, Richard Tyler, Michael Gayford, Roger Derry
The cochlea is a snail-shaped bony structure containing a spiral tube divided along its length by two membranes (Figure 1.50). The two outer channels (scala vestibuli and scala tympani) are connected by a small opening (the helicotrema), at the apical end of the cochlea and are filled with perilymph which is high in potassium ions and at zero electrical potential. The stapes footplate leads into the scala vestibuli at the basal end where it also interconnects with the vestibular system. At the basal end of the scala tympani is situated the round window opening covered by a thin membrane exposed to the middle ear cavity. As the cochlear fluids and walls are effectively incompressible, an inward motion of the stapes produces an outward motion of the round window membrane.
Chapter 3 Physics of the Senses
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
The membrane separating the scala tympani from the cochlear duct is called the basilar membrane (see figure 3.15), and the motion of this membrane plays a key role in the generation of the nerve impulses associated with the sense of hearing. The basilar membrane runs the full length of the spiral, and spans across from a bony shelf to a ligament. The membrane contains many fibres, each approximately 1–2 µm in diameter, that run spanwise across it. The length of these fibres varies from approximately 75 µm near to the oval window up to about 475 µm at the helicotrema. Inside the cochlear duct, and supported on the basilar membrane, is the organ of Corti. It is this organ that accomplishes the transformation of mechanical to electrical energy.
Study of fatigue damage to the cochlea
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Lei Gao, Jiakun Wang, Junyi Liang, Wenjuan Yao, Lei Zhou, Xinsheng Huang
The BM is given in Figure 3. The BM in the cochlea is a linear elastic material, and its modulus of elasticity has been measured in previous experiments to decrease gradually from the base to the apex, here from 600 MPa (base) to 10 MPa (apex). The perilymph fluid in the scala vestibular and scala tympani of the cochlea is a low viscosity compressible fluid, which was measured to be similar to water with a density of 1000 kg/m3 and a viscosity coefficient of 0.001 Ns/m2. The fluid-structure interface is indicated as the junction between the inner surface of the cochlear duct and the BM. The inlet boundary is at the oval window, the inlet boundary condition is a given pressure, and the outlet boundary is at the round window, its condition is fixed at a pressure 0 constraint. In the model calculation, the initial liquid condition is 0. The controlling equation for the fluid is: where is the fluid density, is the fluid velocity, is the dynamic viscosity coefficient, is the pressure, is the volume force density on the solid, I is 3rd order unit matrix, and K is the dissipation function containing the compressible term, T express matrix transpose.