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Sound field, spatial hearing, and sound reproduction
Published in Bosun Xie, Spatial Sound, 2023
The inner ear mainly consists of the cochlea, a bony-wall tube with a coiled (shelled) structure of approximately 2.75 turns. The length of the uncoiled cochlea is approximately 35 mm. The end close to the oval window is called the base, and the other end is called the apex. The cochlea is divided by two membranes, i.e., the basilar membrane and Reissner’s membrane, into three chambers: the scala vestibuli, the scala media, and the scala tympani (Figure 1.10). The scala vestibuli and scala tympani, filled with the perilymph, are connected by a small hole at the apex, that is, the helicotrema. Two openings exist between the middle ear and the cochlea: the oval window attached to the stapes and the round window (sealed by a membrane) located at the bony wall of the scala tympani.
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.
Introduction to Hearing
Published in Douglas Self, Audio Engineering Explained, 2012
Input acoustic vibrations result in a piston-like movement of the stapes footplate at the oval window which moves the perilymph fluid within the cochlea. The membrane covering the round window moves to compensate for oval window movements since the perilymph fluid is essentially incompressible. Inward movements of the stapes footplate at the oval window cause the round window to move outwards and outward movements of the stapes footplate cause the round window to move inwards. These movements cause traveling waves to be set up in the scala vestibuli which displace both Reissner's membrane and the basilar membrane.
A comprehensive finite element model for studying Cochlear-Vestibular interaction
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Junfeng Liang, Zhang Ke, Paige V. Welch, Rong Z. Gan, Chenkai Dai
All the surfaces of the components that had visible geometry (SCCs, vestibule, bony structures) in the CT images after reconstruction in Amira were translated into HyperMesh (Altair Computing, Inc., Troy, MI) to generate FE meshes for the inner ear components (Figure 1a). The soft tissues that did not possess a clear boundary in the μCT images, such as BM, Reissner’s membrane (RM), and cupulas were subsequently added based on visual observation, and the descriptions of them in the literature (Rask-Andersen et al., 2011) Figure 1(b) shows that the inside structure of the chinchilla cochlea. The three ducts in the cochlea divided by the membranous labyrinth, the scala tympani (ST), scala media, and scala vestibuli (SV) were built inside the cochlea cavity in the FE model based on the outline of the bony structure (Muller et al. 2010). The real geometry of the support bony structure was irregular and exhibited wavy surfaces. A simplified treatment of the shape and thickness of them was adopted in the model. The support bony structure was assumed to be a constant thickness and connected the BM and the RM to form the boundary of the three ducts. The outer bony shell of the cochlea and vestibule was simplified as a fixed boundary at the external surface of perilymph in the vestibular system and the external surface of ST and SV. The membranous labyrinth of the vestibule was modeled as a thin layer of brick element (Solid185) separating the vestibule and the SCCs as two liquid-filled compartments: endolymph and perilymph (Figure 1c). The endolymph in the vestibule was connected with the SM in the cochlea with a narrow entrance. Note that in this model saccule and utricle were simplified as one combined vestibular compartment due to the lack of detailed anatomical knowledge of chinchilla vestibule. Figure 1(d) shows the inside structure of the SCCs including the threes cupulas modeled as solid geometries lie at the three ampullas respectively. An interspace about 50 µm (Swan 2018) was kept from the tip of the cupulas to the ampulla walls in the model to avoid complex simulation of the contact between them.