Biomedical subjects

A Tubis

Publications and source records attributed to A Tubis.

23 records · Page 2Linked to original sources

PubMed1985

Incidence of spontaneous otoacoustic emissions in children and infants.

Whereas some evidence indicates that spontaneous otoacoustic emissions (SOAEs) may be a manifestation of the normal functioning of an active feedback mechanism in the cochlea, other evidence suggests that emissions may be the result of the interaction of such a feedback mechanism with localized outer-hair-cell damage. The present study surveyed the incidence of SOAEs in children and infants. If SOAEs are correlated with outer-hair-cell damage, the incidence of SOAEs might be expected to be lower in these two groups than in adults. The results showed no difference in the incidence of SOAEs with age. They also showed a significant tendency for a higher incidence of SOAEs in females than in males.

Aging↗

PubMed1984

Interactions among spontaneous otoacoustic emissions. I. Distortion products and linked emissions.

Spontaneous otoacoustic emissions (SOAEs) can be recorded from human ears with a sensitive microphone in the ear canal. The evidence to date strongly indicates that the origin of these emissions in an active electro-mechanical process at the basilar membrane level. In this report we present data on interactions among SOAEs in ears with multiple SOAEs, including: intermodulation distortion products, mutual suppression, and noncontiguous-linked SOAEs which apparently share energy between two quasi-stable states. These results demonstrate the highly nonlinear and extremely complex nature of the active process, and present a challenge for mathematical modeling of the mechanisms involved.

Acoustics↗

PubMed1983

Frequency-domain investigations of cochlear stability in the presence of active elements.

For a linear, time-invariant cochlear response function, the requirements of causality and stability imply the absence of poles of the spectral response function g(omega) for Im omega greater than 0, with e-i omega t as the time-dependent factor. The existence of such poles invalidate conventional Hilbert transform (dispersion) relations. The testing of these dispersion relations provides a frequency-domain check of system stability for cochlear models which contain active elements such as negative resistance. The stability of several one- and two-dimensional cochlear models with active elements is checked using these dispersion relations. A simple circuit analog of the cochlea, which contains active elements, is used to illustrate the relationship between the pole locations of g(omega) and the strength of active elements.

Cochlea↗

PubMed1983

Effects of perilymph viscosity on low-frequency intracochlear pressures and the cochlear input impedance of the cat.

Cochlear model calculations are shown to be in reasonable agreement with recent low-frequency measurements of intracochlear pressures and the cochlear input impedance of the cat [V. Nedzelnitsky, J. Acoust. Soc. Am. 68, 1676-1689 (1980); T. J. Lynch, III, V. Nedzelnitsky, and W. T. Peake, J. Acoust. Soc. Am. 72, 108-130 (1982)]. Included in the cochlear model are perilymph viscosity, the measured variation of the area of the scala vestibuli with distance from the stapes [P. Dallos, J. Acoust. Soc. Am. 48, 489-499 (1970)], and finite impedance of the round window membrane. The WKB approximation and its extension to the low-frequency region is used in order to exhibit explicitly the dependence of the model results on the cochlear parameters.

Acoustic Impedance Tests↗

PubMed1982

Implications of causality, time-translation invariance, linearity, and minimum-phase behavior for basilar membrane response functions.

Several implications of the assumptions of causality (C), time-translation invariance (TTI), linearity (L), and minimum phase behavior (MPB) for basilar membrane (BM) frequency-response functions are derived. They are then used to: (1) test the consistency of calculated results for a two-dimensional cochlear model [S. T. Neely, J. Acoust. Soc. Am 69, 1386-1393 (1981)] and (2) check experimental data on the BM displacement/malleus displacement [W, S. Rhode, J. Acoust. Soc. Am. 67, 1969-1703 (1980)] for approximate consistency with these assumptions. Both the theoretical model results and experimental cochlear-partition response data are in fairly good accord with these assumptions.

Acoustics↗