Measurement of distortion product phase in the ear canal of the cat. 1997

P F Fahey, and J B Allen
Department of Physics, University of Scranton, Pennsylvania 18510, USA.

Amplitudes of odd order distortion products (DPs) that are detected in animal ear canals have been used to probe cochlear health, to search for cochlear amplification, and to measure aspects of cochlear mechanical frequency response. Like the DP amplitude, DP phase is also an important measure of the cochlear mechanical response. Reported here are measurements of DP phase in the ear canal of the cat. The phase data show frequency-dependent time delays. One of these delays is a function of f2, the frequency of the higher-frequency primary. Hence the DP phase phi d is of the form phi d = phi 0 + omega d tau, where omega d is the DP angular frequency and tau is a fixed time delay. Our results show that phi d is independent of input level a2 as long as the ratio a2/a1 < or = 2, where a2 and a1 are the amplitudes of the input tones. As a2/a1 becomes greater than two, the fixed time delays increase for DPs whose frequencies are less than the frequencies of the input tones. When both levels are varied together the delay increases as the levels decrease. There can be phase changes as large as pi associated with deep nulls in the DP magnitude for the two lower-frequency DPs. Features of the nulls may be modeled assuming that there is partial reflection of the DP wave from the DP place. The assumption of energy remitted from the DP place also explains amplitude-ratio-dependent time delays and 2 pi level-dependent bifurcations in phase. The DP phase shows different dependencies for f2 < 1 kHz compared to f2 > 2 kHz.

UI MeSH Term Description Entries
D002415 Cats The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801) Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D003051 Cochlea The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH. Cochleas
D004424 Ear Canal The narrow passage way that conducts the sound collected by the EAR AURICLE to the TYMPANIC MEMBRANE. Auditory Canal, External,External Acoustic Canal,External Acoustic Meatus,External Auditory Canal,External Ear Canal,Acoustic Canal, External,Acoustic Canals, External,Acoustic Meatus, External,Auditory Canals, External,Canal, Ear,Canal, External Ear,Canals, Ear,Canals, External Ear,Ear Canal, External,Ear Canals,Ear Canals, External,External Acoustic Canals,External Auditory Canals,External Ear Canals
D000161 Acoustic Stimulation Use of sound to elicit a response in the nervous system. Auditory Stimulation,Stimulation, Acoustic,Stimulation, Auditory
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013997 Time Factors Elements of limited time intervals, contributing to particular results or situations. Time Series,Factor, Time,Time Factor

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