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Biomedical subjects

D T Kemp

Publications and source records attributed to D T Kemp.

46 records · Page 3Linked to original sources
PubMed1984

Ear canal acoustic and round window electrical correlates of 2f1-f2 distortion generated in the cochlea.

Close parallels have been found between the behaviour of the distortion product 2f1-f2 measured acoustically in the meatus (ACDP) and the 2f1-f2 component (CMDP) measured in the gross cochlear electrical response from the round window during two-tone stimulation. The two response modes show comparable growth with increasing stimulus intensity. Their group latencies and their frequency-selective susceptibility to suppression by a third tone are very similar. The common origin of these two responses is discussed.

Acoustic Stimulation↗
PubMed1982

Intradermal use of human diploid cell vaccine for preexposure rabies immunizations.

In a study involving 240 faculty, students, and staff at the University of Georgia College of Veterinary Medicine, 0.1 ml of a rabies human diploid cell vaccine administered intradermally on days 0, 7, and 28 induced adequate rabies antibody (greater than or equal to 0.5 IU/ml of serum) in all subjects by day 49. There were no significant differences in mean titers between groups of individuals with different rabies immunization histories by using a newly proposed index system for reporting such titers. It was shown that if there was a titer on the day the initial dose was given, it had no bearing on the titer 49 days later. Less than 1% of all the injections resulted in severe reactions, ie, muscular pain, headache, or pain at the site of injection. It was concluded that intradermal use of a low dose of rabies human diploid cell vaccine will induce adequate antibody titers in persons at risk to rabies.

Adult↗
PubMed1981

Physiologically active cochlear micromechanics--one source of tinnitus.

Spontaneous oscillatory vibrations within the cochlea exist in many normal ears and can become audible, providing one source of mild tonal tinnitus. These vibrations have been studied experimentally using an acoustic ear-canal recording technique. The spontaneous oscillations are directly related to stimulated acoustic emissions (cochlear echoes). They arise because of the development of strong cochlear resonances by a feedback process. With the aid of cochlear resonance theory the bandwidths of spontaneous cochlear mechanical activity can be used to determine intracochlear broad-band noise levels. Ways of modifying cochlear mechanical activity have been explored. Activity can be increased or decreased by changes in middle-ear mobility or by brief overstimulation. In the latter case a biphasic recovery cycle has been identified which also seems to be relevant to temporary noise-induced tinnitus and temporary threshold shift. Tinnitus due to spontaneous cochlear vibrations is here called cochlear mechanical tinnitus. Identification criteria are given for such tinnitus involving cochlear mechanical resonance. This form is mild and likely to be found in normally hearing people with tinnitus and in those with only middle-ear disorders. It is speculated that localized oscillation of mechanically isolated cochlear elements could induce much higher levels of tinnitus without producing any externally detectable vibration.

Acoustic Stimulation↗
PubMed1980

Properties of the generator of stimulated acoustic emissions.

In Part I, the sound emitting properties of the peripheral auditory system are briefly reviewed and links with other literature are cited. (Summary of Symposium section introduction). In Part II, the stimulation of acoustic emissions by clicks is examined experimentally and analytically, in order to specify the physical qualities and parameters of the unknown generator which may be considered as driving the ear drum. Special attention is paid to absolute magnitudes to the qualitative interpretation of the generator's nonlinear properties and to the extent of inter-stimulus interactions in the time and frequency domains. New transient suppression results are presented. From the observations made, and without reference to the likely cochlear origin of the phenomenon, it is deduced that the generator is a multiple channel system, with each channel consisting of at least a steep-sloped narrow band filter followed by a fast acting compressive nonlinearity. A secondary nonlinearity seems also to be present, of a form which requires the filter itself to be nonlinear. The maximum power output of the generator is of the order 0.26 X 10(-12) W.

Basilar Membrane↗
PubMed1979

Evidence of mechanical nonlinearity and frequency selective wave amplification in the cochlea.

A previously unsuspected mechanical response of the cochlear transduction mechanism has recently been discovered. It can be monitored outside the cochlear. Theorectical and experimental work leading to its discovery and identification are briefly reviewed. Its significance for models of the second filter and cochlear nonlinearity is discussed. An active wave amplification mechanism in the cochlea is proposed.

Acoustic Stimulation↗
PubMed1979

The evoked cochlear mechanical response in laboratory primates. A preliminary report.

The evoked cochlear mechanical response has been recorded in two species of laboratory primates, Macaca irus and Erythrocebus patas. The responses are very similar to those obtained in humans although the response to each click is of shorter duration. The response is vulnerable to the ototoxicity of furosemide and etacrynic acid and to noise exposure. At and near threshold an active generator of mechanical energy within the cochlea is proposed. The significance of such a generator and a possible source are discussed.

Animals↗
PubMed1978

Stimulated acoustic emissions from within the human auditory system.

A new auditory phenomenon has been identified in the acoustic impulse response of the human ear. Using a signal averaging technique, a study has been made of the response of the closed external acoustic meatus to acoustic impulses near to the threshold of audibility. Particular attention has been paid to the waveform of the response at post excitation times in excess of 5 ms. No previous worker appears to have extended observations into this region. The response observed after about 5 ms is not a simple extension of the initial response attributable to the middle ear. The oscillatory response decay time constant was found to change from approximately 1 ms to over 12 ms at about this time. The slowly decaying response component was present in all normal ears tested, but was not present in ears with cochlear deafness. This component of the response appears to have its origin in some nonlinear mechanism probably located in the cochlea, responding mechanically to auditory stimulation, and dependent upon the normal functioning of the cochlea transduction process. A cochlear reflection hypothesis received some support from these results.

Acoustic Impedance Tests↗