PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 6826462

Sharp vibration maximum in the cochlea without wave reflection.

J J Zwislocki
View original source ↗Export metadata ↓

Abstract

The recently discovered sharp vibration maximum of the basilar membrane at the best frequency is difficult to reconcile with the reflectionless traveling wave that is implied by the empirical data. The apparent paradox is resolved by representing the cochlea as a transmission line and investigating its characteristic impedance. The appropriate differential equation has been derived previously (Zwislocki, J. (1953); J. Acoust. Soc. Am. 25, 986-989). It is valid for both long and short wave lengths found in the cochlea. The investigation reveals that, in the presence of sufficiently short waves prevailing around the vibration maximum, the characteristic impedance remains practically constant, independent of the rapid variation of the impedance of the basilar membrane. Since wave reflection depends on variation of the characteristic impedance, no wave reflection should be expected. The constancy of the characteristic impedance also enhances the vibration maximum.

Explore related subjects

Basilar MembraneCochleaHumansMathematicsOrgan of CortiScala TympaniTectorial MembraneVibrationJournal ArticleResearch Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J J Zwislocki. 1983. Sharp vibration maximum in the cochlea without wave reflection.. https://doi.org/10.1016/0378-5955(83)90138-7

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1995

On equivalence of locally active models of the cochlea.

In the literature on locally active models of the cochlea several forms of the model have been worked out in which elements of the organ of Corti are assumed to produce acoustical energy. In these models use is made of a secondary resonance or a place-dependent delay to achieve activity over a limited part of the length of the basilar membrane, and outer hair cells are postulated as sources of energy production. In the present paper it will be shown that several of these models are formally equivalent. That means that they can be reduced to a standard form, and that the only difference resides in the choice and meaning of the parameters. The results of the analysis serve to facilitate the analysis of function and structure in cochlear models containing sources of local activity. In particular, questions of positive versus negative feedback, and the parts played by resonance and impedance-level differences can be resolved unambiguously. The treatment can be extended to models with higher dimensionality, and can also serve to obtain insight in nonlinear phenomena occurring in cochlear models.

Basilar Membrane↗
PubMed1994

Distortion product otoacoustic emissions in an active nonlinear model of the cochlea.

An active nonlinear model of the cochlea in the form of a transmission line was presented, in which the active feedback system by outer hair cells (OHCs) was expressed as a series of low-pass filters on the basilar membrane (BM) which were transducing basilar membrane displacement to feedback force. The model could produce distortion product oto-acoustic emissions (DPOAEs) explicitly as well as sharp tuning curves of BM, and it was possible to discuss the cause of DPOAEs in terms of the active feedback. It was inferred that the nonlinearity of the cochlea which causes DPOAEs may be related to a saturating property of the feedback system by OHCs.

Basilar Membrane↗
PubMed1994

Modeling the fine structure of the 2f1-f2 acoustic distortion product. II. Model evaluation.

In a previous article, a vector sum model was developed that successfully reproduces the ADP rippling pattern when a nonuniformity is introduced in the active damping factor, a parameter that is inversely related to the energy gain contribution of the outer hair cells [OHCs, Sun et al., J. Acoust. Soc. Am. 96, 2166-2174 (1994)]. Here, the mean of the damping factor is increased nonlinearly with input level, mimicking the saturation of the active feedback of the OHCs. The passive damping factor in the transmission line model was also nonlinearly increased with input level to reproduce the frequency shift of the peak of the traveling wave observed in experimental data. The resulting model simulates an ADP that is compatible with data from human subjects wherein the ADP fine structure does not saturate with level. Moreover, the model suggests that the shifting of the ADP pattern with level is a direct result of the peak shift of the traveling wave, thus implicating the nonlinear damping factors as the underlying basis of this phenomenon. The input/output (I/O) functions of the simulated ADP emissions at specific frequencies were also examined. The resulting functions show a variety of shapes, depending on the pattern of ADP fine structure around the I/O frequency, and the way the fine structure shifts as primary levels increase. These I/O functions are also similar to those observed in human subjects, even with regard to overall slopes which approximate one. Thus the model illustrates how cubic distortion generators coupled with damping on linearities can yield I/O function slopes on the order of one, rather than the expected three.(ABSTRACT TRUNCATED AT 250 WORDS)

Basilar Membrane↗