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Simultaneous Measurement of the DPOAE Signal Amplitude and Phase Changes

Michalski W., Bochnia M., Dziewiszek W.

Archives of Acoustics

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2011

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Vol. 36, No. 3

499-508

EN

Although the phenomenon of otoacoustic emission has been known for nearly 30 years, it has not been fully explained yet. One kind of otoacoustic emission is distortion product of the otoacoustic emission (DPOAE). New aspects of this phenomenon are constantly discovered and attempts are made to interpret correctly the obtained results. This paper discusses a new method of measuring DPOAE signals based on double phase-sensitive detection, which makes possible a real-time measurement of the DPOAE signal amplitude and phase. The method was applied for measurements of DPOAE signals in guinea pigs. Sample records are presented and the obtained results are discussed.

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Wpływ niskich dawek gentamycyny na ucho wewnętrzne u świnki morskiej

Dziewiszek W., Bochnia M., Michalski W.

Prace Naukowe Instytutu Telekomunikacji i Akustyki Politechniki Wrocławskiej. Konferencje

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2001

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Vol. 83, nr 27

319-323

EN

First reports on ototoxicity of medicines were published by Kirchner (1883) and Wittmaack (1903). Gentamicin is the most frequently used aminoglycoside of the second generation. Experimental doses of gentamicin reach even 200 mg/kg, and their ototoxicity is proven. The aim of work was an estimation of the tuner ear sensory cells after administration of minimal doses of the antibiotic. The control group consisted of 10 guinea pigs, which were given 2 ml/kg of 0.9 % NaCl. The experimental group consisted also of 10 animals. They were given gentamicin 25 mg/kg i.m., once a day for 10 consecutive days. After completion of the experiment, cochlear microphonics with modified phase-sensitive detection technique were received. They were done for 6 frequencies from 260 Hz to 8 kHz, and 4 levels of acoustic impulse pressure from 55 to 95 dB. Next, the cochleae were prepared for examination in a scanning electron microscopy. Significant differences between the cochlear microphonics in both groups were not found. In all animals correct pictures of sensory cells were also observed, but in the experimental animals disturbances of microphonics phase for the frequencies 2, 4, and 8 kHz were detected. This may be indicative of cochlear frequency position changes in the submicroscopically injured inner ear.

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Badania dynamiki działania wibracji ogólnej na narząd Cortiego

Bochnia M.

Prace Naukowe Instytutu Telekomunikacji i Akustyki Politechniki Wrocławskiej. Konferencje

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2001

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Vol. 83, nr 27

307-311

EN

Most investigations of the effect of vibration on the organ of hearing represent results of long-term observation. A significant decrease of cochlear microphonics was observed in animals subjected to whole-body vibration. Results of short-term experiments were ambiguous. The aim of this experiment was to estimate the dynamics of the effect of whole-body vibration on cochlear microphonics in guinea pigs. 18 animals in 3 groups of 6 each were subjected to sinusoidal perpendicular vibration (10 Hz/5 mm/ 1.4 g rms) in a noiseless vibrational apparatus for 1 day (6 h), 10 days (60 h), and 30 days (180 h). After completion of the experiments, in every animal bilaterally, cochlear microphonics with a modified phase-sensitive detection technique were measured. The measurements were done for 6 frequencies from 260 Hz to 8 kHz using levels of acoustic impulse pressure of 70, 80, and 90 dB. For the 18 measuring - points (definite frequency and level of tone pressure) a decrease of microphonics was observed in 66% of the cases. In 33% (after 1 or 10 days of vibration) an increase (in comparison with the control group) was present. As statistical analysis of the obtained results indicates, the short-term experiments should not be taken into account in investigations of the harmfulness of vibration for the hearing organ.

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Badania doświadczalne przemieszczeń dynamicznych ślimaka świnki morskiej

Dobrucki A., Abramski K., Bochnia M., Dziewiszek W.

Prace Naukowe Instytutu Telekomunikacji i Akustyki Politechniki Wrocławskiej. Konferencje

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2001

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Vol. 83, nr 27

313-318

EN

The guinea pig is frequently used as an experimental animal in the examination of vibratory disorders of the hearing organ. Its bony cochlea is found on the medial wall and projects into the tympanic bulla. In man, the cochlea is totally situated in the petrous part of the temporal bone. These anatomical differences may be responsible for the interspecies dissimilarities in the manner of their dynamic dislocations. The aim of the investigation was to see whether the cochlea of a guinea pig subjected to whole-body vibration vibrates as a rigid body. We sought differences between the inclinations of the base and the top of the cochlea attached to an exciter and subjected to perpendicular sinusoidal vibrations of the frequencies 50, 100, 300 and 500 Hz. We investigated five temporal bones received from animals weighting from 350 to 670 g. We measured oscillations with an interference technique using Michelson's interferometer. Two beams of light were emitted from a He - Ne laser (wave length of 632 nm). The first fell on the examined object, the other on a motionless mirror. After reflection, both beams interfered. We registered the interference stripes by means of a digital oscilloscope and counted using a impulse meter. No essential differences between the amplitudes of the inclinations of the top and cochlea base were detected. This means that the cochlea of the guinea pig vibrates as a rigid body. The animal selected can be useful in experiments of vibratory damages of the ear.