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At least 19 recordsLinked to original sources
PubMed2004

Semicircular canal fenestration - improvement of bone- but not air-conducted auditory thresholds.

Auditory stimulation can, under certain circumstances, activate the vestibular end organs and this is facilitated by fenestration of a semicircular canal (SCC). Several fenestrated profoundly deaf patients reported improvements in their bone- (BC) but not air-conducted (AC) thresholds. Bone conduction auditory thresholds have been reported to be better than normal in several patients with thinning or absence of bone over a SCC (dehiscence). This phenomenon was carefully studied in the fat sand rat (Psammomys obesus) by recording auditory brainstem evoked responses to BC and AC auditory stimulation, before and after SCC fenestration. Fenestration would be expected to decrease the pressure difference across the cochlear partition, causing a reduction in the amplitude of the classical base to apex input traveling wave, and should therefore lead to an elevation in AC and BC thresholds. Instead, BC thresholds decreased (i.e. improved) following fenestration (by 7.0+/-4.2 dB; P<0.005), while AC thresholds did not change. Thus the cochlea becomes more sensitive to BC, but not AC, stimulation in the presence of a SCC fenestration. This may be due to the removal by the fenestration of a factor impeding BC cochlear responses, or by the addition of a facilitating factor. The result that the SCC fenestration did not affect AC threshold provides support for the concept that at low intensities the outer hair cells are directly activated by components of the fluid pressures surrounding them, which alternate at audio-frequencies. These cochlear fluid audio-frequency pressures are induced by stapes footplate movement and not by a base to apex input traveling wave. The audio-frequency pressures would not be affected by SCC fenestration. The outer hair cell motility thus induced somehow excites the inner hair cells and the auditory nerve fibers. At low intensities the outer hair cell motility causes localized displacement at the appropriate position on the basilar membrane.

Acoustic Stimulation↗
PubMed2006

Does peripheral auditory threshold correlate with brainstem auditory function at term in preterm infants?

CONCLUSION: Peripheral auditory threshold does not correlate with brainstem auditory function in preterm infants. Infants with peripheral auditory abnormality seem not to be necessarily more prone to brainstem auditory abnormality than those without the elevation, although further studies are needed in a larger number of subjects. OBJECTIVE: To investigate whether peripheral auditory threshold correlates with brainstem auditory function in preterm infants and shed light on whether preterm infants with threshold elevation are prone to central auditory abnormality. PATIENTS AND METHODS: Brainstem auditory evoked response (BAER) was recorded with clicks at term in preterm infants (gestation 28-36 weeks). Analysis of correlation was made between BAER threshold and various BAER components. BAER data were compared between preterm infants with thresholds < or = 20 dB nHL (n = 113) and those > 20 dB (n = 32). RESULTS: Although BAER threshold correlated significantly with BAER wave latencies and amplitudes, the threshold did not correlate significantly with I-V, I-III and III-V intervals. No significant differences were found between preterm infants with BAER thresholds < or = 20 dB and those > 20 dB in I-V, I-III intervals, although III-V was longer in the infants with thresholds > 20 dB nHL (p < 0.05).

Audiometry, Evoked Response↗
PubMed2005

Auditory brainstem responses in the Eastern Screech Owl: an estimate of auditory thresholds.

The auditory brainstem response (ABR), a measure of neural synchrony, was used to estimate auditory sensitivity in the eastern screech owl (Megascops asio). The typical screech owl ABR waveform showed two to three prominent peaks occurring within 5 ms of stimulus onset. As sound pressure levels increased, the ABR peak amplitude increased and latency decreased. With an increasing stimulus presentation rate, ABR peak amplitude decreased and latency increased. Generally, changes in the ABR waveform to stimulus intensity and repetition rate are consistent with the pattern found in several avian families. The ABR audiogram shows that screech owls hear best between 1.5 and 6.4 kHz with the most acute sensitivity between 4-5.7 kHz. The shape of the average screech owl ABR audiogram is similar to the shape of the behaviorally measured audiogram of the barn owl, except at the highest frequencies. Our data also show differences in overall auditory sensitivity between the color morphs of screech owls.

Acoustic Stimulation↗
PubMed1984

Effects of the ovarian and contraceptive cycles on absolute thresholds, auditory fatigue and recovery from temporary threshold shifts at 4 and 6 kHz.

Absolute thresholds at 4 and 6 kHz were tested in three sessions before and after 20 min of exposure to 105 dB(A) pink noise in 12 young normal-cycling females, 11 young females on oral contraceptives and 8 young men. Women on contraceptives showed lower resting thresholds, larger temporary threshold shift (TTS) and higher recovery rates than normal-cycling females. The analysis of resting thresholds, auditory fatigue and recovery from auditory fatigue did not evidence any sex-linked difference. Significant differences linked to the phases of the menstrual cycle and of the contraceptive cycle were observed during recovery from auditory fatigue at 4 kHz and in resting thresholds at 6 kHz. Application of Kendall's coefficient of concordance confirmed these results. Absolute thresholds were highest at menstruation and lowest in the postovulatory phase in normal-cycling females and in women on oral contraceptives, during the days of pill ingestion. Oral contraception is probably a more important factor of change in hearing performance than the phases of the menstrual cycle.

Adult↗
PubMed1987

Estimation of auditory threshold during sleep using brainstem auditory-evoked potentials.

The brainstem auditory-evoked potential (BAEP) is often employed to determine auditory threshold in subjects who are unable to complete traditional behavioural testing. These responses are usually recorded during natural or drug-induced sleep. The effects of sleep on the BAEP threshold have however not been determined. BAEPs were recorded in 8 young adults in wakefulness and during natural sleep. Click stimuli were presented through a hearing aid device at either 0, 5, 10, 20 or 30 dB above the behavioural threshold. The amplitude of wave V decreased and its latency increased with decreases in stimulus intensity. The BAEP waveform was invariant in sleep. The overall mean BAEP threshold was approximately 16 dB above that determined by behavioural methods. This did not significantly vary in the sleeping subject.

Adult↗
PubMed1978

Longitudinal study of hearing in children: baseline data concerning auditory thresholds, noise exposure, and biological factors.

Serial auditory thresholds are being recorded at six-month intervals from 224 children and youths aged 4--18 years. The data from the first year show girls have lower threshold levels than boys, especially from 12--17 years, and, in both sexes, those aged 12--17 years have lower thresholds than those aged 6--11 years. Median total noise exposure scores tend to be higher in boys than girls, especially after 10 years of age, but these scores are not significantly correlated with auditory thresholds levels. The incidence of exposure to events associated with noise increases markedly in teenage boys and is related to auditory threshold levels. There are no significant associations between auditory thresholds levels and responses to general health questions or attained stature, but there are associations with meatal abnormalities. There is suggestive evidence, particularly in girls, that rapid maturation is associated with lower threshold levels, especially at lower frequencies.

Adolescent↗
PubMedDate not supplied

[Auditory threshold for white noise].

The liminal auditory threshold for white noise and for coloured noise was determined from a statistical survey of a group of 21 young people with normal hearing. The normal auditory threshold for white noise with a spectrum covering the whole of the auditory field is between -- 0.57 dB +/- 8.78. The normal auditory threshold for bands of filtered white noise (coloured noise with a central frequency corresponding to the pure frequencies usually employed in tonal audiometry) describes a typical curve which, instead of being homothetic to the usual tonal curves, sinks to low frequencies and then rises. The peak of this curve is replaced by a broad plateau ranging from 750 to 6000 Hz and contained in the concavity of the liminal tonal curves. The ear is therefore less sensitive but, at limited acoustic pressure, white noise first impinges with the same discrimination upon the whole of the conversational zone of the auditory field. Discovery of the audiometric threshold for white noise constitutes a synthetic method of measuring acuteness of hearing which considerably reduces the amount of manipulation required.

Adolescent↗
PubMed1975

Auditory thresholds and the effect of reduced auditory feedback of suttering.

The effects of reduced auditory feedback were investigated using an accurately calibrated binaudal pure tone producer on 27 stuttering children and 68 non-stuttering controls. A comparison was made of both auditory hearing and discomfort thresholds in the two groups; the hearing thresholds did not differ between the groups. The results did however replicate an earlier finding which suggested that stutters have a lower threshold for auditory discomfort than do normal speakers, and showed that fluency is inversely related to auditory feedback. The discussion suggests that a necessary cause of stuttering is a physiological abnormality in side-tone conduction and central processing.

Adolescent↗
PubMed1985

[Application of a response duration schedule in rats to evaluate visual and/or auditory threshold].

Determination of visual and auditory thresholds was carried out under a response duration schedule of tone and/or light-dipper presentation. This schedule enabled an exact assessment of visual and auditory sensitivities, since the direction and distance from the rat to the sound or light sources were constant, and the rat could thus acquire the conditioned behavior in a short time. The rat has to put its nose into the hole and hold it there until a conditioned stimulus (tone and/or light) was presented. The animal could get water-reinforcement by taking its nose out from the hole during the period of conditioned stimulus. To determine the visual threshold, the intensity of light was reduced, from 100 Lx (starting point) by 10 Lx steps in each trial, until the subject made 10 non-response trials (i.e., no dipper approach within 1.0 sec after the light onset) among 10 trials. In terms of auditory threshold, the intensity of 3, 7 and 10 KHz pure tone was reduced, from 90 dB by 10 or 2 dB steps in each trial, until the subject made 10 non-response trials among 10 trials. The light or tone intensity that prolonged the response latency 2 times compared to normal rats was taken as the threshold. The visual sensitivity in the rats suffering from alkaline-burn on its corneas decreased about 14 Lx. The auditory thresholds in rats were 19.5 +/- 1.3, 37.5 +/- 1.8 and 54.6 +/- 1.3 dB at 10, 7 and 3 KHz, respectively. The auditory sensitivity in the rats with cotton-stuffed ears and pierced eardrums decreased about 6 and 12 dB, respectively.

Animals↗
PubMed2001

Effects of exercise and noise on auditory thresholds and distortion-product otoacoustic emissions.

Differences in auditory thresholds and distortion-product otoacoustic emission (DPOAE) levels were investigated as a function of gender, ear, frequency, and experimental condition: quiet sedentary activity, exercise, noise, and exercise and noise combined. In general, participants displayed significant elevations in auditory thresholds of approximately 6 to 13 dB following the two conditions employing noise exposure. There were no significant differences in either auditory threshold differences before and following the quiet and exercise conditions or between the noise-alone and combined exercise and noise conditions. Participants also displayed significant reductions in DPOAE levels of approximately 6 to 7 dB following the two conditions employing noise exposure. The findings also showed no gender or ear effects on auditory threshold or DPOAE level differences. Further, there was no evidence of a synergistic combination of exercise and noise on auditory function as revealed by changes in hearing threshold or DPOAE levels.

Adult↗
PubMed1996

Evaluation of TEOAE and DPOAE measurements for the assessment of auditory thresholds in sensorineural hearing loss.

Transiently evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) can be quantified concerning their amplitude and frequency. They are known to be diminished or absent in sensorineural hearing loss. It is therefore of interest how TEOAE and DPOAE correlate with the auditory threshold and whether the auditory threshold can be predicted by these variables. In a cross sectional study of 61 patients (102 ears) with sensorineural hearing loss, auditory threshold, tympanometry, stapedius reflexes, TEOAE and DPOAE were measured. Correlation coefficients of the hearing loss (0.5-6 kHz) and the amplitude of the distortion product 2f1-f2 (0.46 4 kHz) respectively TEOAE amplitude (1-4 kHz) were computed. TEOAE showed lower correlation coefficients and less frequency specificity than DPOAE. In order to increase the correlations with the auditory threshold we fitted a multivariate linear regression model with TEOAE and DPOAE simultaneously as predictors for the auditory threshold gaining 95% prediction intervals of 19-39 dB depending on the frequency investigated. By restricting the hearing loss to a maximum of 70 dB HL the 95% prediction interval of the auditory threshold could be decreased to 18-26 dB. Further improvements can be expected if the high inter- and intraindividual variability of TEOAE and particularly DPOAE measurements can be reduced. The results allow us to use TEOAE and DPOAE in addition to click-evoked brainstem audiometry in order to provide more frequency specific information about the hearing loss in newborns, which is of the utmost importance for an ideal fitting of hearing aids.

Acoustic Impedance Tests↗
PubMed2006

The effects of positive and negative middle ear pressures on auditory threshold.

HYPOTHESIS: To assess the effects of positive and negative middle ear pressures on auditory threshold. BACKGROUND: Nonatmospheric middle ear pressures can alter auditory threshold by their effects on tympanic membrane and ossicular chain mobility. METHODS: Experiments were conducted on guinea pigs by inducing alterations in pressure (positive and negative) with a syringe connected to the middle ear bulla cavity, the magnitude of the pressure being assessed with a water manometer. Elevated middle ear fluid pressures were also induced by attaching a saline-filled vertical tube to the saline-filled middle ear. The effect of these altered middle ear air and fluid pressures were assessed by recording auditory nerve-brainstem evoked responses. RESULTS: There was no effect on auditory threshold of positive middle ear air pressures (up to 250 mm H2O). A negative middle ear air pressure of -50 mm H2O induced a significant 9.5-dB threshold elevation, whereas more negative pressures (up to -150 mm H2O) did not induce an additional threshold elevation. Filling the middle ear cavity with saline induced a 10- to 16-dB elevation, whereas additional fluid pressures (up to 200 mm H2O) did not induce further elevations. CONCLUSION: The major factor inducing threshold elevation in serious otitis media is not the alteration in middle ear pressure but rather the reduction in the volume of compressible air in the middle ear by the fluid.

Air Pressure↗
PubMed2001

Hair cell regeneration and recovery of auditory thresholds following aminoglycoside ototoxicity in Bengalese finches.

Birds regenerate auditory hair cells when original hair cells are lost. Regenerated hair cells become innervated and restore hearing function. Functional recovery during hair cell regeneration is particularly interesting in animals that depend on hearing for vocal communication. Bengalese finches are songbirds that depend on auditory feedback for normal song learning and maintenance. We examined the structural and functional recovery of the Bengalese finch basilar papilla after aminoglycoside ototoxicity. Birds were treated with the ototoxic aminoglycoside, amikacin, daily for 1 week. Treatment resulted in hair cell loss across the basal half of the basilar papilla and corresponding high frequency hearing loss. Hair cell regeneration and recovery of auditory brainstem responses were compared in the same animals. Survival times following treatment were between 1 day and 12 weeks. Analysis of structural recovery at weekly intervals indicated that hair cells in the Bengalese finch papilla require a maximum of 1 week to regenerate and appear with immature morphology at the epithelial surface. An additional 6 days are required for adult-like morphology to develop. Repopulation of the damaged region was complete by 8 weeks. Recovery of auditory thresholds began 1 week after treatment and reached asymptote by 4 weeks. Slight residual threshold shifts at 2.0 kHz and above were observed up to 12 weeks after treatment. Direct comparison of structural and functional recovery indicates that auditory thresholds recover maximally before a full complement of hair cells has regenerated.

Amikacin↗
PubMed2001

Auditory threshold reduction on alcohol ingestion.

RATIONALE: Auditory threshold (AT) measurement method has become the standard behavioral procedure for describing auditory sensitivity. Therefore, the AT measurement method is applicable to evaluation of auditory function. However, only a few studies have been performed to clarify the alteration of audibility under the influence of alcohol on normal humans by measurement of AT. OBJECTIVE: The fact that blood alcohol concentration (BAC) is influenced by the dose of alcohol and the time of measurement suggests that the effects of alcohol may also be altered by the same factors. The present study was conducted to elucidate how alcohol ingestion method affects the AT at a wider range from lower to higher frequency in the time course. METHODS: Fifteen paid Japanese (seven men and eight women, 20-33 years of age) were employed in AT measurements at an octave frequency ranging from 250 to 8,000 Hz before and 5, 30, 60, 120, 240 and 480 min after drinking various amounts (125, 250, 500 and 1,500 ml) of normal beer (5% alcohol) or alcohol-free beer. RESULTS: The AT was significantly reduced within 30 min after the ingestion of 250 and 500 ml of beer, occurring on and after peak BAC. The reducing effect disappeared 480 min after ingestion. CONCLUSIONS: Drinking extra small amounts of alcohol induces the reduction of AT. The effect of alcohol on AT is altered by the alcoholic dose used in testing.

Adult↗
PubMed2000

Auditory threshold and inner ear pressure: measurements in experimental endolymphatic hydrops.

HYPOTHESIS: Experimental endolymphatic hydrops leads to an endolymph-perilymph pressure imbalance that is responsible for the loss of auditory sensitivity in the ear. BACKGROUND: This study investigates whether intralabyrinthine pressure is a factor in the auditory dysfunction of experimental endolymphatic hydrops. METHODS: Auditory function was investigated in 10 guinea pigs 90 to 120 days after endolymphatic sac ablation by measuring compound action potentials in response to acoustic stimuli including alternating clicks and tone bursts of 0.5, 1, 2, 4, and 8 kHz. After auditory thresholds to the various stimuli were established, endolymphatic and perilymphatic pressures were measured with a no-flow micropressure measuring system. The cause of the hearing loss in Meniere's disease, especially in the early phases of this condition, remains an enigma. Histologic temporal bone preparations show a disproportion in the volume of endolymph to perilymph with an expanded and distorted membranous labyrinth. Speculation as to whether an endolymph-perilymph fluid pressure imbalance is responsible for these morphologic changes were raised by Hallpike and Cairns (1) in their initial report of the histopathology of Meniere's disease. Further speculation has questioned whether this pressure imbalance may be responsible for the symptoms and physical finding of this condition, including hearing loss. The ability to produce experimental endolymphatic hydrops in the guinea pig secondary to surgical occlusion of the endolymphatic sac and duct has been useful in studying various aspects of Meniere's disease (2). Investigators have been able to demonstrate auditory threshold shifts with hydrops. Elevated endolymph-perilymph pressure gradients have also been demonstrated (3). This RESULTS: Increased auditory thresholds were noted in the hydrops ears at all tested parameters (p < 0.03). A relative increase in endolymph over perilymph pressure was found in hydrops ears as previously reported. The increase in endolymph-perilymph pressure of hydrops could not be correlated directly to the elevated auditory threshold shift. CONCLUSION: Endolymphatic hydrops is a complex pathologic state with multiple inner ear alterations including abnormal intralabyrinthine pressure. Factors other than or in addition to pressure contribute to the auditory threshold shift of hydrops.

Animals↗
PubMedDate not supplied

Trimethyltin disrupts loudness recruitment and auditory threshold sensitivity in guinea pigs.

Trimethyltin (TMT) impairs auditory thresholds within minutes of systemic administration. However, there are no data which relate to the output of the auditory nerve at sound levels above threshold. In this experiment, we evaluated the functional effects of TMT on the auditory threshold by identifying the sound level which just produced a detectable compound action potential (CAP). We also assessed outer hair cell function by measuring the cochlear microphonic (CM), a nonpropagated ac potential which is phase-locked to the stimulus. Finally, we measured the growth of the N1 amplitude as a function of stimulus intensity at levels above threshold and of the summating potential (SP), a dc potential which has multiple generators. To isolate cochlear from systemic effects of TMT, the agent was applied directly to the round window, a structure separating the middle and inner ear, of anaesthetized guinea pigs. We show that TMT applied to the round window membrane can disrupt the function of the cochlea. Measurements of auditory function at supra-threshold levels showed clearly that TMT reduced the amplitude of N1 while having no measurable effect on the SP. These findings indicate that TMT blocks the recruitment of neuronal elements by loud sound. This pattern of impairment differs from that observed with aminoglycoside antibiotics, hypothermia, and presbycusis in which loudness recruitment has been reported.

Action Potentials↗