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Otoacoustic emission (OAE) data recorded for tone bursts presented separately and as a two-tone burst complex, that had been reported previously [Yoshikawa, H., Smurzynski, J., Probst R., 2000. Suppression of tone burst evoked otoacoustic emissions in relation to frequency separation. Hear. Res. 148, 95–106], were re-processed using the method of adaptive approximations by matching pursuit (MP). Two types of stimuli were applied to record tone burst OAEs (TBOAEs): (a) cosine-windowed tone bursts of 5-ms duration with center frequencies of 1, 1.5, 2 and 3kHz, (b) complex stimuli consisting of a digital addition of the 1-kHz tone burst together with either the 1.5-, 2- or 3-kHz tone burst. The MP method allowed decomposition of signals into waveforms of defined frequency, latency, time span, and amplitude. This approach provided a high time–frequency (t–f) resolution and identified patterns of resonance modes that were characteristic for TBOAEs recorded in each individual ear. Individual responses to single-tone bursts were processed off-line to form ‘sum of singles’ responses. The results confirmed linear superposition behavior for a frequency separation of two-tone bursts of 2kHz (the 1-kHz and 3-kHz condition). For the 1, 1.5-kHz condition, the MP results revealed the existence of closely positioned resonance modes associated with responses recorded individually with the stimuli differing in frequency by 500Hz. Then, the differences between t–f distributions calculated for dual (two-tone bursts) and sum-of-singles conditions exhibited mutual suppression of resonance modes common to both stimuli. The degree of attenuation depended on the individual pattern of characteristic resonance modes, i.e., suppression occurred when two resonant modes excited by both stimuli overlapped. It was postulated that the suppression observed in case of dual stimuli with closely-spaced components is due to mutual attenuation of the overlapping resonance modes.

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Otoacoustic emissions (OAEs) are generated in the cochlea in response to sound and are used clinically to separate ears with normal hearing from sensorineural hearing loss (SNHL). OAEs were elicited at ambient pressure by clicks (CEOAE) and wideband chirps (TEOAE) sweeping from low-to-high frequency with a sweep rate of either 187.6 Hz/ms (short chirps) or 58.2 Hz/ms (long chirps) and a bandwidth extending to 8 kHz. Chirps were presented at the same sound exposure level (SEL) as clicks, or + 6 dB relative to clicks. A total of 288 OAE waveforms were averaged for short chirps in ~1 minute compared to 120 waveforms for long chirps. Compared to clicks, the chirp has a lower crest factor, which allows it to be presented at an overall higher SEL without distortion. OAEs were elicited in 79 adults with normal hearing and 51 adults with mild-to-moderate SNHL. One-sixth octave OAE signal-to-noise ratios from 0.7 to 8.0 kHz were compared across stimulus types and conditions. The area under the receiver operating curve (AUC) was used to assess the accuracy of detecting SNHL. Average AUCs across 1/6th octave frequencies ranged from 0.90 to 0.89 for TEOAEs and were 0.87 for the CEOAE suggesting excellent test performance.

Previous studies have shown that supplemental magnesium administered prior to exposure to noise has an alleviating effect on temporary threshold shift (TTS). These studies have only used audiometric thresholds to demonstrate changes in the auditory system. However, to help determine the effects on outer hair cells (OHCs), a more sensitive measure should be used. The purpose of this study was to determine if supplemental magnesium administration prior to noise exposure has a beneficial effect on acoustic overexposure using a double-blind research design. This was determined by measuring distortion product otoacoustic emissions (DPOAEs) to determine any changes in cochlear OHC function. DPOAE amplitude and signal-to-noise ratio (SNR) measurements were analyzed for two groups of twenty participants (an experimental group and a control group). The experimental group received 150 mg of magnesium gluconate one hour prior to noise exposure. The control group received a placebo pill that was identical in appearance to the magnesium pill. Following noise exposure, the greatest changes in DPOAE amplitude and SNR occurred for the frequencies that were one-half to one octave above the frequency of the stimuli used. The greatest changes in DPOAE measurements were present immediately post TTS-inducing stimulus, with only slight changes present after 30 minutes and no difference between 30 minutes and 60 minutes post-exposure. These results were the same for both groups. It was concluded that this dosage of supplemental magnesium had no apparent protective effect on DPOAEs following intense noise exposure.

Professional research project (Au.D.)--University of South Florida, 2002. / Title from PDF of title page. / Document formatted into pages; contains 48 pages. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: This paper provides an overview of developmental timetables relevant to hearing and of current pediatric audiological techniques and practices. The first sections summarize structural and functional development of the auditory pathway and the development of primary auditory processing. These developmental sequences appear to follow similar paths in humans and animals. Speech and music perception involve more complex processing and are strongly influenced by experience. Hearing disorders affect the perception of complex sounds in a variety of ways, depending on the site(s) of lesions. Early onset hearing impairment, including conductive loss from chronic otitis media, can seriously impede language development. Language cannot develop normally without adequate speech stimulation. / ABSTRACT: Sensitive and inexpensive techniques are available for performing neonatal hearing screening, and early intervention has a positive effect on development of language skills in hearing-impaired children. Thus, the National Institute of Health has recommended nationwide universal newborns hearing screening. The rationale and methodology of universal screening programs is summarized in the chapter. Advances in the field of the genetics of hearing impairment are also reviewed / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.