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At least 811 records · Page 45Linked to original sources
PubMed1996

Limitations in the use of distortion product otoacoustic emissions in objective audiometry as the result of fine structure.

There is strong evidence for a link between intact cochlear function and otoacoustic emissions (OAE). However, all attempts to find a close correlation between auditory thresholds and amplitudes of distortion product otoacoustic emissions (DPOAE) have failed. As an explanation for these findings, we have studied DPOAE fine structure and its dependence on increasing primary sound levels. Errors due to different calibrations of equipment for measuring DPOAE and auditory thresholds were also investigated. DPOAE were measured in 16 subjects using a frequency range of 500-1000 Hz. Frequencies were changed in 12.5 Hz steps at primary levels of 55, 60, 65 and 70 dB SPL. DPOAE amplitudes were found to vary by up to 20 dB for a frequency step of 50 Hz. Some fine structures showed narrow dips that shifted in frequency and diminished in amplitude with increasing primary levels. These findings demonstrated that sampling DPOAE amplitudes at widely spaced frequencies gave incomplete information about true course. DPOAE growth functions measured close to a dip in the DPOAE fine structure were rendered useless by interference with either the frequency shift or amplitude variations of the dip at different primary levels.

Acoustic Stimulation↗
PubMed1975

[Problems of the electric response audiometry (ERA) during the natural and artificial sleep (author's transl)].

The investigators carried out threshold determinations on 16 children and 6 adults in wakefulness, under general anaesthesia (we used chloral hydrate anaesthesia) and in sleep (stage II-III and stage REM). Falling asleep (stage I and initial stage of anaesthesia respectively) the latencies of the individual components of the acoustically evoked potentials are prolonged in mean of 30 msec. Simultaneously the amplitude of N1 significantly decreases and N2 becomes a prominent point (Fig. 1). The generation mechanisms of wave N2 are obviously different from those of wave N1. Its input-output curve takes a very steep course (Fig. 5) and the shortening of latencies increases with growing intensity of stimulus too (Fig. 4). Amplitude histogrammes demonstrated the dependency of the form of the acoustically evoked potential on the degree of synchronisation of EEG activity. While in the case of desynchronisation N1 appears more markedly, N2 does in the case of synchronisation. The mean deviation of the ERA threshold totals plus 3.8 +/- 6.9 dB (n = 41) under chloral hydrate anaesthesia, plus 4.9 +/- 6.7 dB (n = 37) in natural sleep in contrast to the wakefulness. With a 99% confidence there occur confidence intervals ranging from + 1 to + 7 dB and from +2 to +8 dB respectively. In identifying the threshold potentials error I (existing potential not recognized) occurred in 15-20%, error II (random wave seen as potential) in 20% of these studies. All these experiments showed significant lower variances for the latencies compared with variancies of amplitudes. The variance of amplitudes is smallest in children (Table 1) under general anaesthesia as well as in adults in wakefulness (Table 2). For the practical performance of ERA chloral hydrate is recommended for studies on children. A uniform EEG-state as well as a uniform depth of sleep are basic conditions for ERA during sleep, sedation or under anaesthesia. These conditions must constantly be controlled by EEG, EOG and EMG.

Adult↗
PubMedDate not supplied

Brain stem electric response audiometry in neonates with hyperbilirubinemia.

Auditory evoked responses using BERA were studied in 30 newborn babies with plasma bilirubin > or = 15 mgm/dl and repeated after treatment of neonatal jaundice with bilirubin levels of < or = 10 mgm/dl. A few jaundiced babies (16.5%) showed absent BERA response at the initial/subsequent examination. After treatment, 3/30 babies showed absent wave form responses and 2 of these were clinically kernicteric. Jaundiced babies had prolonged wave peak latencies and inter peak latencies. Treated babies showed a tendency towards recovery in their BERA responses which were however not complete. Total plasma bilirubin value at the time of BERA examination and mean maximal bilirubin values had no correlation with the incidence and degree of BERA abnormalities.

Audiometry, Evoked Response↗
PubMed2004

[Speech perception. The basis for speech audiometry examinations].

Speech recognition measurements are widely used in clinical applications. Usually, either a speech recognition threshold is determined, being defined as the speech level or signal-to-noise ratio that enables the patient to understand 50% of the target words or target sentences. In other cases, a discrimination curve, describing speech recognition as function of the presentation level, is recorded. For the interpretation of these findings, it is important to keep in mind that speech perception is affected by many interacting sensory, perceptual and cognitive processes.Here, our current knowledge of these processes is outlined and theories that model speech perception in general are briefly reviewed.

Audiometry, Speech↗
PubMed2006

Relationship between CT densitometry with a slice thickness of 0.5 mm and audiometry in otosclerosis.

The appropriate cutoff Hounsfield unit (HU) value for the diagnosis of otosclerosis was determined and the correlation between the bone conduction threshold and the findings of computed tomography (CT) densitometry investigated. CT images, 0.5-mm thick, were evaluated in 24 ears with otosclerosis and 19 control ears. Eight regions of interest were set around the otic capsule. The mean HU values in the area anterior to the oval window (A-OW) and anterior to the internal auditory canal (A-IAC) were significantly lower in otosclerosis than in controls. Based on receiver operating characteristic (ROC) analysis, the cutoff HU value in A-OW was determined to be 2,187.3 HU. The mean HU value in retrofenestral otosclerosis was significantly lower in the area A-OW, A-IAC and around the cochlea than in controls. Based on ROC analysis, the cutoff HU value in the latter was determined to be 2,045 HU. A statistically significant correlation was found between the density of the area A-OW and the hearing level at 500 and 1,000 Hz, and between the density of the area around the cochlea and the hearing level at most frequencies. These results suggest the semi-automated diagnosis of otosclerosis may be possible.

Absorptiometry, Photon↗
PubMed1978

On-line statistical detection of average evoked potentials: application to evoked response audiometry (ERA).

An objective method of EP detection in averaged EEG epochs is described which is based on the statistical properties of the averaged EEG in the absence of time-locked EP activity. The statistical properties of the subject's averaged background EEG are summarized by making a set of comparisons between two consecutive EEG epochs immediately preceding each stimulus presentation. After every stimulus presentation, a second set of comparisons is made between the post-stimulus EEG epoch and the immediately preceding pre-stimulus EEG epoch. These two sets of comparisons are then examined to determine whether the latter differ significantly from the former. The technique has been programmed for on-line use on a 12-bit minicomputer, validated on cooperative adult subjects and used for ERA threshold determinations in young children. Using response detection criteria yielding an empirically determined false positive error rate of between 1 and 4%, threshold estimates averaged about 10 dB higher than psychophysical thresholds. The efficiency with which such ERA thresholds may be obtained with this method is substantially greater than that of conventional ERA procedures employing subjective evaluation of averages. Further, the technique allows variation of detection criteria to suit non-audiometric needs and empirical determination of the false-positive error rate under any set of conditions.

Adult↗
PubMed1984

Weighted averaging--theory and application to electric response audiometry.

A weighted averaging technique has been developed to overcome the shortcomings of conventional, unweighted averaging in the case of nonstationary noise. The technique is based on the linear least-mean-square estimate of a periodic signal in a simple model of non-stationary noise. This estimate weights each recorded epoch according to the magnitude of the noise within the epoch. In the estimation of a known signal, the weighted averaging procedure yielded smaller root-mean-square errors in comparison with the normal unweighted average. The weighted averaging procedure offers many advantages over conventional averaging or averaging with automatic gain control preamplifiers.

Audiometry↗
PubMed1983

Discrimination of auditory from nonauditory toxicity by reflex modulation audiometry: effects of triethyltin.

The evaluation of toxicity in sensory systems presents particular problems because of the need to distinguish specific sensory loss from other toxic effects. It has recently been shown that modulation of reflex behavior by low-intensity test stimuli can be used to provide a rapid assessment of sensory acuity and of ototoxic hearing loss. In this report the ability of the method to distinguish the known neuromuscular consequences of triethyltin (TET) from hearing loss is demonstrated. Rats treated with TET bromide (30 mg/liter) in their drinking water for 3 weeks showed a profound decrease in acoustic startle reflex amplitudes which was apparent prior to overt neuromuscular weakness and subsequent hindlimb paralysis. Following cessation of treatment, startle levels recovered to preexposure values. Despite these large changes in startle reflex amplitudes, TET treatment did not alter the ability of pure tone stimuli to modulate reflex behavior. These results indicate that TET as administered in these studies disrupted neuromuscular function but did not affect hearing.

Analysis of Variance↗
PubMed1980

Free field pure tone audiometry as a comparative system for the assessment and fitting of hearing aids.

In this brief report it is shown that without the use of language and/or complex tones, it has been possible to determine whether or not the potential of residual hearing is being fully utilized by the hearing impaired child or adult with or without an aid. Furthermore, because the system is one of direct and immediate comparison it can be used to confirm if the initial selection of a specific hearing prosthesis is potentially correct.

Adult↗
PubMed1988

Inter-stimulus interval in audiometry for neonates.

The usual paradigm employed for both clinical and experimental evaluation of auditory responsiveness of newborns dictates that signal presentations be separated by a minimum of 15 s. Furthermore, this paradigm requires that there be 8 presentations of the signal and that two responses among the 8 trials should be taken as normal responsiveness. Many have been concerned about accepting 25% as normal, and would prefer a paradigm that could lead to increased responsiveness. A procedure with inter-stimulus intervals longer than 15 s might be that paradigm. Therefore, the following experiment employed inter-stimulus intervals of 15, 30 and 60 s to examine responsiveness of infants young enough to be in a newborn nursery. Each infant received 24 signal presentations (8 with each of the 3 inter-stimulus intervals), and these were counter-balanced across babies. Although there is evidence of response habituation across time, there is also evidence that longer inter-stimulus intervals do lead to increased responsiveness.

Acoustic Stimulation↗