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At least 1,027 records · Page 57Linked to original sources
PubMed1991

Repeatability of transiently evoked otoacoustic emissions in normally hearing humans.

Transiently evoked otoacoustic emissions (TEOAEs) were stimulated using clicks. Responses were measured in each ear of 10 adult subjects during three test sessions separated by 3-day intervals. The purpose was to determine the amount of short-term variability in the amplitude of the emissions when measured under similar test conditions. For each of two modes of determining the stimulus level, mean overall response levels varied approximately 1 dB with repeated measurements. The spectra of the responses were analyzed in discrete frequency bands from 0.7 to 5.8 kHz. Response energy peaked at 1.2 kHz and was reduced markedly above 4 kHz. Variability within individual spectral bands was approximately 1 dB from 0.9 to 4.1 kHz and was slightly greater for 0.7 kHz. The amplitude of TEOAEs is stable over successive short-term measurements. The technique can be used as a sensitive means of monitoring cochlear function.

Adult↗
PubMed1991

Evoked otoacoustic emissions: correlates between spectrum analysis and audiogram.

Correlations between spectrum analysis of evoked otoacoustic emissions (EOAEs) and hearing losses have been calculated in 150 patients with pure sensorineural hearing loss. Significant correlations were found. The greater the high-frequency spectral components of the EOAE, the better the high-frequency hearing. However the relationship is complex, and it does not seem possible to establish an audiogram knowing only the spectrum analysis of EOAEs.

Adult↗
PubMed1992

Growth of evoked otoacoustic emissions during the first days postpartum. A preliminary report.

Evoked otoacoustic emissions (EOAEs) were recorded twice in 20 ears of 15 newborns. The recordings were performed in a room of the well baby ward, using the ILO88 in its default setting, i.e. with click stimulation. On the first test occasion, the infants were between 3 and 51 h of age, and EOAEs were identified in 10 ears. On the second test occasion, while the infants were at least 1 day older (range 42-107 h), EOAEs were present in all ears. The second EOAE was stronger, so the EOAE appeared to grow in the first days postpartum. This might be due to middle ear clearance of amniotic fluid, shortly after birth. The results of the EOAEs of the second examination were compared with 10 EOAEs in adult ears. The response levels of the newborns were significantly higher than in the adults. The (cross)-correlation peak value of the two tests' waveforms is over 0.75, however sometimes only after filtering around the most pronounced emission frequencies. The study proves that newborns failing the EOAE screen in the first 24 h after birth can pass if retested 1 day later, simply because of growth of EOAE strength.

Acoustic Stimulation↗
PubMedDate not supplied

Cochlear delays and traveling waves: comments on 'Experimental look at cochlear mechanics'.

In a recent publication [Audiology 1992;31:301-312], A. Dancer argued that direct and indirect measures of basilar membrane motion are more consistent with theories of cochlear resonance than with the traveling-wave theory. The present communication reviews empirical evidence that contradicts Dancer's argument. Such evidence--recordings of mechanical responses of the basilar and Reissner's membranes to sound--strongly supports the existence of displacement waves that propagate on the basilar membrane from the base of the cochlea toward its apex.

Acoustic Stimulation↗
PubMedDate not supplied

Auditory neuropathy with preserved cochlear microphonics and secondary loss of otoacoustic emissions.

Auditory neuropathy is defined as absent or severely distorted auditory brainstem responses with preserved otoacoustic emissions and cochlear microphonics. This entity can be found in various circumstances including pre-lingual children. An almost universal characteristic reported from adult patients is the ineffectiveness of traditional hearing aids. Adequate management of pre-lingual cases therefore remains an open problem. This paper describes two pre-lingual children whose follow-up data demonstrated a selective loss of the otoacoustic emissions, whereas the cochlear microphonics remained preserved. In one of the patients, hearing aid fitting as soon as she lost her otoacoustic emissions proved successful. These findings have important implications for the operational definition of the condition, since one must be prepared to encounter cases with absent otoacoustic emissions. The present data also demonstrate that conventional amplification can benefit pre-lingual auditory neuropathy cases, at least once they have lost their otoacoustic emissions.

Adult↗
PubMed1990

Quality estimation of click-evoked oto-acoustic emissions.

The Fsp statistic used by Elberling & Don (1984) as a quality estimator for averaged ABR recordings has been applied to averaged click-evoked oto-acoustic emissions. This statistic is akin to signal-to-noise ratio. The sampling distribution of Fsp under the null hypothesis that no signal is present has been determined by using no-stimulus trials. A determination by multiple replications in three normally-hearing adults demonstrated significant inter-subject variation, leading to a larger experiment in 58 children. From the latter experiment, the sampling distribution across subjects allowed the setting of a criterion value for Fsp of 2.0 which was only exceeded on 1% of trials. Thus, values above this criterion would indicate the presence of a signal in the average with a probability of Type I error below 1%. When two consecutive average both exceeded an Fsp of 1.6 the probability of Type I error was also below 1%.

Adult↗
PubMed1992

Place-specific derived cochlear microphonics from human ears.

The high-pass noise masking technique was used to obtain derived frequency-specific cochlear microphonics (CM) from subtracted waveforms to rarefaction and condensation stimuli recorded with a tympanic membrane electrode. Two characteristics suggest that the response is place-specific CM: the derived response retains the same frequency as the stimulating toneburst and the response follows the stimulus polarity. For click stimulation, derived neural responses make the place-specific CM difficult to observe except in the 2-1 kHz derived band. In contrast, place-specific CM evoked by 0.5 and 1 kHz tonebursts can usually be detected in at least three derived bands. The amplitude of the response is largest in the derived band with center-frequency (CF) just above that of the toneburst. This discovery of a place-specific CM offers the possibility of assessing (outer) hair cell function in the apical part of the human cochlea.

Acoustic Stimulation↗
PubMed1993

The feasibility of evoked otoacoustic emissions as an in-patient hearing check after meningitis.

The desirability of finding children with hearing impairment after bacterial meningitis as soon as possible prompted us to examine the feasibility of using evoked otoacoustic emissions (EOAE) as an in-patient check of hearing status in children recovering from bacterial meningitis. Sixty-six episodes of bacterial meningitis were studied. Traces could be recorded for only 54.7% of ears. All children subsequently found to have sensorineural hearing impairment who were tested with EOAE, failed the screening test. The low coverage of the screening test and the predicted low specificity due to the high incidence of conductive hearing impairments, lead us to conclude that, with the technology currently available, the measurement of EOAE after bacterial meningitis is not a practical method for a pre-discharge check of hearing. Every effort must still be made to ensure all children are referred for an appropriate auditory assessment.

Adolescent↗
PubMed1993

Frequency analysis of the contralateral suppression of evoked otoacoustic emissions by narrow-band noise.

The influence of noise bandwidth on the contralateral masking of click-evoked otoacoustic emissions was investigated by recording emissions from 20 normal subjects with contralateral narrow-band noise, with wide-band noise and without contralateral noise for comparison. Narrow-band noise of five different centre frequencies and three different bandwidths per frequency was used at intensities of 40 and 60 dB SL. Analysis of the emissions showed that the 40-dB SL contralateral noise did not produce a significant amount of suppression. The suppression produced by 60-dB SL noise was spread throughout the frequency range of the emissions, with limited frequency specificity. There was some evidence that the amount of suppression increases with the bandwidth of the noise, particularly for noises centred on 1 and 2 kHz; the wide-band noise produced much greater suppression than any of the narrow bands. There was a large amount of inter-subject variation, which could not be explained by differences in the absolute level of the emissions. One subject with a total unilateral hearing loss in the contralateral ear was also tested, and gave no significant suppression.

Acoustic Stimulation↗
PubMed1995

Evaluation of functionality of cochlear outer hair cells in patients with retinitis pigmentosa and in their relatives.

Hearing functionality was studied in 36 patients with retinitis pigmentosa (R P) and 29 of their relatives. These patients were defined as having bilateral normal hearing on the basis of tonal-threshold audiometric and acoustic-immittance tests. The transiently evoked otoacoustic emissions (T E O A Es) were studied in these normal hearing patients. T E O A Es represent an extremely sensitive method to study the functionality of the outer hair cells of the organ of Corti. When the values of T E O A E amplitude, intensity, and frequency in R P patients and in their relatives were compared with those in control subjects, they were found to be significantly reduced. The T E O A Es were clearly pathological in 52.8% of patients with R P and in 24.1% of their relatives. During embryologic development, there is one transitory axoneme in the outer hair cells of the organ of Corti; this transitory axoneme is important for the organization of the stereocilia. Axonemes are found in mature hair cells, including photoreceptors. The alteration of cochlear outer hair cells in a high percentage of patients with R P and in some of their relatives corroborates the hypothesis that, in some instances, retinitis pigmentosa may be due to a structural anomaly of the ciliated cells.

Adolescent↗
PubMed1997

[Suppression tuning characteristics of the 2f1-f2 distortion product in cochlear microphonics and otoacoustic emissions].

Suppression of the 2f1-f2 distortion product (DP) by the third tone was measured in cochlear microphonics (CM) and otoacoustic emissions (OAEs) in guinea pigs to clarify the generation site of the DPs. The DPs were elicited by the primary tones with frequencies of 4.62 kHz (f1) and 6 kHz (f2). Five dB-iso-suppression tuning curves (STCs) of the DPs were obtained by plotting the suppressor level as a function of its frequencies. The STCs in both CM DP and DPOAE had the shape of the letter "V" with the tip centering around the frequency of f2. The slopes of the STC on the higher frequency side were steeper than those on the lower side. As the intensity of the primary tones was decreased, the turning of the STC became sharper. These suppression properties indicate that the 2f1-f2 DPs were generated in the area on the basilar membrane where the characteristic frequency corresponded to those of primary tones, especially for the primaries at lower intensities. Because the suppression properties in CM DP and DPOAE were similar to each other, we concluded that these two phenomena had a common generation site.

Acoustic Stimulation↗