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Results for “Auditory Threshold”

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At least 505 records · Page 28Linked to original sources

PubMed1978

[Application of a response duration schedule in rats to evaluate drug-induced auditory impairment (author's transl)].

Determination of auditory threshold was carried out under a response duration schedule of tone and/or light-dipper presentation. This schedule enabled an exact assessment of auditory sensitivity, since the direction and distance from rat to sound source were constant and the rat could thus acquire the conditioned behavior in a short time. The rat has to press the lever and hold it until a CS(tone and/or light) was presented. The animal could get water-reinforcement with release of the lever during the period of CS. The intensity of 3 KHz pure tone was reduced, from 110 dB (starting point), by 2 dB steps in each trial, until the subject made 3 non-response trials (i.e., no dipper approach within 0.7 sec after the tone onset) among 5 trials. The highest tone intensity among non-response trials was taken as the threshold. The auditory sensitivity of the rats with cotton-stuffed ears and the pierced eardrums decreased about 10 and 20 dB, respectively. The auditory sensitivity in rats was decreased by administration of streptomycin sulfate(SM), 300 mg/kg/day, i.m., in combination with ethacrynic acid(EA), 50 mg/kg/day, p.o., for forty days and in combination with EA, 100 mg/kg/day, p.o. for ten days. The auditory sensitivity was not influenced by administration of SM, 300 mg/kg/day, i.m., for forty days.

Acoustic Stimulation↗

PubMed1985

Thresholds for primary auditory fibers using statistically defined criteria.

The discharge behavior of auditory-nerve fibers near "threshold" was investigated in anesthetized cats using low-intensity sinusoidal stimuli presented at the respective characteristic frequencies. Particular attention was paid to fibers with "low" and "medium" rates. Estimates of threshold derived from statistically significant increases in discharge rate indicate that the average threshold values for low-spontaneous fibers are only slightly higher (ca. 5 dB) than the averages for the corresponding high-spontaneous fibers, with the medium-spontaneous fibers having intermediate averages. The difference between these average values is considerably less than the more than 20-dB difference obtained using threshold criteria based on an absolute increment in discharge rate [e.g., M. C. Liberman, J. Acoust. Soc. Am. 63, 442-455 (1978)]. The main reason for the difference between the results of the two techniques is the fact that the slopes of the rate-intensity functions for the high-spontaneous fibers are considerably steeper near "threshold" than those for fibers of the other two classes. The results are taken as supportive of a recent model of primary-fiber discharge [C. D. Geisler, Brain Res. 212, 198-201 (1981)].

Animals↗

PubMedDate not supplied

[Course of the audiometric threshold in relation to the age in chronic acoustic trauma].

Until now the relationship between auditory threshold and age has been evaluated in normal subjects only. In this study the Author reports results obtained in a cross-sectional study on 416 subjects suffering from noise-induced hearing loss who were exposed to noise for 10 years at least. The results show that hearing loss over time was more correlated to age than to noise exposure. Moreover, the evolution of hearing loss over time had a linear shape while in noise-induced hearing loss evolution has a logarithmic shape and in presbyacusis it has an exponential shape. The differential threshold between 30 and 60 years obtained by applying the linear regression model was, at higher frequencies, significantly reduced compared to normal subjects. These results suggest that threshold values related to age obtained in normal subjects can not be applied in subjects affected by noise-induced hearing loss.

Adult↗

PubMed2000

Moth hearing in response to bat echolocation calls manipulated independently in time and frequency.

We measured the auditory responses of the noctuid moth Noctua pronuba to bat echolocation calls which were manipulated independently in time and frequency. Such manipulations are important in understanding how insect hearing influences the evolution of echolocation call characteristics. We manipulated the calls of three bat species (Rhinolophus hipposideros, Myotis nattereri and Pipistrellus pipistrellus) that use different echolocation call features by doubling their duration or reducing their frequency, and measured the auditory thresholds from the A1 cells of the moths. Knowing the auditory responses of the moth we tested three predictions. (i) The ranking of the audibility of unmanipulated calls to the moths should be predictable from their temporal and/or frequency structure. This was supported. (ii) Doubling the duration of the calls should increase their audibility by ca. 3 dB for all species. Their audibility did indeed increase by 2.1-3.5 dB. (iii) Reducing the frequency of the calls would increase their audibility for all species. Reducing the frequency had small effects for the two bat species which used short duration (2.7-3.6 ms) calls. However, the relatively long-duration (50 ms), largely constant-frequency calls of R. hipposideros increased in audibility by 21.6 dB when their frequency was halved. Time and frequency changes influence the audibility of calls to tympanate moths in different ways according to call design. Large changes in frequency and time had relatively small changes on the audibility of calls for short, largely broadband calls. Channelling energy into the second harmonic of the call substantially decreased the audibility of calls for bats which use long-duration, constant-frequency components in echolocation calls. We discuss our findings in the contexts of the evolution of both bat echolocation call design and the potential responses of insects which hear ultrasound.

Animals↗

PubMedDate not supplied

Audiometric results following endolymphatic sac surgery.

Decompression and drainage of the endolymphatic sac is a surgical procedure which was developed to relieve vertigo and hopefully to maintain or improve hearing in patients with Meniere's disease. In this study, 16 medically diagnosed Meniere's disease patients who underwent endolymphatic sac surgery were followed audiometrically for a period of up to three years. Pre- and postoperative audiometric and other symptomatic findings were reported. Results indicated that in the greatest majority of cases hearing remained essentially unchanged or was improved. Poorer hearing was found in 26.3% of the cases for pure tones and in 15.8% of the cases for speech reception thresholds and speech discrimination scores. Due to the fluctuating nature of auditory thresholds in Meniere's disease, it was found to be essential that patients be followed postoperatively for a period of at least three years.

Adult↗

PubMed2004

Ultrasonic singing by the blue-throated hummingbird: a comparison between production and perception.

Blue-throated hummingbirds produce elaborate songs extending into the ultrasonic frequency range, up to 30 kHz. Ultrasonic song elements include harmonics and extensions of audible notes, non-harmonic components of audible syllables, and sounds produced at frequencies above 20 kHz without corresponding hearing range sound. To determine whether ultrasonic song elements function in intraspecific communication, we tested the hearing range of male and female blue-throated hummingbirds. We measured auditory thresholds for tone pips ranging from 1 kHz to 50 kHz using auditory brainstem responses. Neither male nor female blue-throated hummingbirds appear to be able to hear above 7 kHz. No auditory brainstem responses could be detected between 8 and 50 kHz at 90 dB. This high-frequency cutoff is well within the range reported for other species of birds. These results suggest that high-frequency song elements are not used in intraspecific communication. We propose that the restricted hummingbird hearing range may exemplify a phylogenetic constraint.

Acoustic Stimulation↗

PubMed1981

P3 latency in threshold signal detection.

The EOG, EEG(Cz, Pz) and response latencies were obtained from ten subjects in an auditory threshold detection task with a signal probability of 0.5. In order to minimize any interaction of signal condition (signal-presence vs. signal-absence) and uncertainty about the moment of signal occurrence (temporal equivocation), the observation period was marked with a cue light. The single-trial latencies of the P3 component associated with correct signal-present and signal-absent decisions were assessed on the basis of the cross-covariance functions of the EEG epochs and a template of the P3. Trials with values of covariance smaller than a criterion value were discarded. The mean and dispersion of the P3 latency proved larger for signal-absent than for signal-present trials, while the mean values of covariance were smaller for signal-absent than for signal-present trials. In addition, the mean and dispersion of the P3 proved smaller for high confidence than for medium confidence signal-present trials. Nearly all these effects also proved significant for the response latency. The single-trial P3 latencies were positively correlated with the response latencies of the same trials. The observed latency variations of the P3 were interpreted in terms of changes in the detectability of the stimulus events. It was concluded that the signal condition had a significant effect upon the latency of the P3 associated with signal-present and signal-absent decisions over and above that due to temporal equivocation.

Adult↗

PubMed1975

Some thoughts on the perception of ultrasonics by man.

After a short specification of the ultrasonic transmitter device by which the test frequencies of 20,40,60 and 100 kHz could be emitted by means of a transmitter fixed to the forehead of the subject with constant pressure, the mean perception threshold for ultrasonics is described, which had been recorded by using the wide-band noise of the audiometer MA 30. Both curves do not differ considerably so that ultrasonic investigations can be carried out in the presence of working noise without producing wrong measurement results. A comparison of perception between ultrasonic frequencies and audio frequencies in the hearing range showed that ultrasonics produce, independent of the stimulation frequency, the same sensory impression as a sound at a frequency of about 12 or 13 kHz. Applying this method to hard of hearing subjects with noise induced hearing damages and deaf subjects had the following results: 1. Subjects with noise induced hearing damages very early have a raised perception threshold for ultrasonics. There was no correlation between the extent of the auditory threshold (the shift of the threshold) and the perception threshold of ultrasonics. 2. Deaf people almost without exception are not able to perceive ultrasonics. 3. With hard of hearing of the inner ear of different genesis ultrasonic perception is varying. There was no particular raise of the ultrasonic perception threshold with hereditary hard of hearing of the inner ear. 4. On the basis of the results the question is discussed in which section of the auditory system ultrasonic perception occurs. In the opinion of the authors the origin of perception might be in the organ of Corti itself. An unambiguous proof, however, could not be found so far. At present the procedure of investigation does not yet allow an application in practical diagnostics of ear specialists.

Adolescent↗

PubMed1994

Hearing preservation in acoustic neuroma surgery.

Hearing conservation in acoustic tumour surgery remains controversial. There have been few previous reports in the British literature. The senior author has managed 24 patients by retrosigmoid surgery with the intention of preserving hearing during the last 9 years. The clinical features, surgical technique and results are discussed with respect to pre-operative selection criteria, and post-operative quality of hearing. Hearing preservation has been achieved in 11 (78.6%) of 14 patients with small or intracanalicular tumours and a mean minimum auditory threshold of 35 dB and 70% speech discrimination, the majority (81.8%) above the 50 dB/50% level. Tumour filing the fundus of the internal auditory canal was found to be a significant adverse prognostic factor as regards successful hearing preservation. Tumour excision was complete in all patients. Nearly 90% of patients had normal facial function, and the remaining 10% grade II function. Associated morbidity was minimal. It is suggested that the potential for hearing conservation should be considered as a factor in the management of patients with small acoustic neuromas.

Adult↗

PubMed2004

Test-retest reliability of pure-tone thresholds from 0.5 to 16 kHz using Sennheiser HDA 200 and Etymotic Research ER-2 earphones.

OBJECTIVE: The purposes of the study were: (1) To evaluate the intrasession test-retest reliability of pure-tone thresholds measured in the 0.5-16 kHz frequency range for a group of otologically healthy subjects using Sennheiser HDA 200 circumaural and Etymotic Research ER-2 insert earphones and (2) to compare the data with existing criteria of significant threshold shifts related to ototoxicity and noise-induced hearing loss. DESIGN: Auditory thresholds in the frequency range from 0.5 to 6 kHz and in the extended high-frequency range from 8 to 16 kHz were measured in one ear of 138 otologically healthy subjects (77 women, 61 men; mean age, 24.4 yr; range, 12-51 yr) using HDA 200 and ER-2 earphones. For each subject, measurements of thresholds were obtained twice for both transducers during the same test session. For analysis, the extended high-frequency range from 8 to 16 kHz was subdivided into 8 to 12.5 and 14 to 16 kHz ranges. Data for each frequency and frequency range were analyzed separately. RESULTS: There were no significant differences in repeatability for the two transducer types for all frequency ranges. The intrasession variability increased slightly, but significantly, as frequency increased with the greatest amount of variability in the 14 to 16 kHz range. Analyzing each individual frequency, variability was increased particularly at 16 kHz. At each individual frequency and for both transducer types, intrasession test-retest repeatability from 0.5 to 6 kHz and 8 to 16 kHz was within 10 dB for >99% and >94% of measurements, respectively. The results indicated a false-positive rate of <3% in reference to the criteria for cochleotoxicity for both transducer types. In reference to the Occupational Safety and Health Administration Standard Threshold Shift criteria for noise-induced hazards, the results showed a minor false-positive rate of <1% for the HDA 200. CONCLUSION: Repeatability was similar for both transducer types. Intrasession test-retest repeatability from 0.5 to 12.5 kHz at each individual frequency including the frequency range susceptible to noise-induced hearing loss was excellent for both transducers. Repeatability was slightly, but significantly poorer in the frequency range from 14 to 16 kHz compared with the frequency ranges from 0.5 to 6 or 8 to 12.5 kHz. Measurements in the extended high-frequency range from 8 to 14 kHz, but not up to 16 kHz, may be recommended for monitoring purposes.

Adolescent↗

PubMed2001

[Early detection of a sensorineural aspect of hypoacusis in patients with chronic purulent otitis media].

To detect initial signs of internal ear dysfunction in 87 patients with otitis media purulenta chronica (OMPC), wide-rage frequency audiometry (WRFA) in bone and air conduction according to B.M. Sagalovich was used. Most of the patients with normal bone conduction in frequencies up to 8 kHz had higher bone thresholds in wide-range frequencies. In mixed hypoacusis these thresholds rose to the highest degree. A correlation was found between a rise of auditory thresholds wide range of frequencies in bone conduction and the disease duration.

Adolescent↗

PubMed1999

Salicylate attenuates gentamicin-induced ototoxicity.

Aminoglycosides, primarily gentamicin, are the most commonly used antibiotics worldwide despite their toxicity to the kidney and the inner ear. A preventive therapy against these side effects should combine safety and efficacy with low cost because aminoglycoside-induced deafness is most prevalent in developing countries. We have previously shown that aminoglycosides catalyze the formation of free radicals in an iron-dependent reaction and have delineated the structure of an iron-gentamicin complex. Here we demonstrate that 2-hydroxybenzoate (salicylate), which can act as an iron chelator and antioxidant, effectively protects against gentamicin-induced hearing loss in guinea pigs. Co-therapy with salicylate reduced a profound gentamicin-induced auditory threshold shift of more than 60 dB to less than 20 dB. Morphological assessment of the inner ear confirmed protection of auditory sensory cells. Salicylate altered neither serum levels of gentamicin nor its antibacterial efficacy. Because the required salicylate levels correspond to anti-inflammatory levels in humans, this treatment holds promise for clinical application.

Administration, Oral↗

PubMed1997

Pathophysiological mechanisms of hearing loss.

An understanding of auditory transduction in the ear can contribute to a better comprehension of the pathophysiological mechanisms which give rise to hearing loss. The incoming sound sets up a mechanical traveling wave which begins at the base and progresses along the basilar membrane, reaching a point of maximal displacement. The region of maximal displacement is a function of stimulus frequency. The mechanical displacement, by directly opening ion channels in the stereocilia of the hair cells, induces changes in the electrical potential of the hair cells. This initial stage is called mechano-electrical transduction, and in the normal ear, is followed by a stage of electro-mechanical transduction based on the ability of the outer hair cells to respond to the electrical changes induced in them with a change in their length. This "electromotility" presumably provides mechanical feedback to the basilar membrane, augmenting its mechanical displacement. This is called the cochlear amplifier, providing the ear with improved sensitivity and frequency discrimination. Most forms of sensori-neural hearing losses (affecting the inner ear) are due to a lesion to some part of this cochlear amplifier (e.g. noise induced hearing loss, ototoxic drugs) and are therefore characterized by auditory threshold elevations and poorer frequency discrimination.

Acoustic Stimulation↗

PubMed1989

Normative thresholds in the 8- to 20-kHz range as a function of age.

Using a prototype high-frequency audiometer, auditory thresholds in the 8- to 20-kHz range were obtained from 240 subjects ranging in age from 10-60 years. These measurements were obtained in interest of developing a normative database for frequencies above 8 kHz, and to evaluate intersubject variability as a function of age. An analysis of variance (ANOVA) revealed significant effects of frequency, age, and sex, and a significant frequency-by-age interaction. The largest changes in sensitivity with age occurred between 40 to 59 years. Below approximately 15 kHz, the intersubject variability of threshold estimates increased as a function of both age and frequency. Further analysis revealed that the age-related changes in variability were related to absolute thresholds rather than to age per se. When data are converted to dB HL (relative to the youngest group tested), the region of maximum hearing loss shifts to lower frequencies with increasing age, and threshold shifts with age are greatest in the 13- to 17-kHz range.

Adolescent↗

PubMed1975

Hearing in the parakeet (Melopsittacus undulatus): absolute thresholds, critical ratios, frequency difference limens, and vocalizations.

Avoidance conditioning and the method of limits were used to measure absolute auditory thresholds, masked thresholds, and critical ratios in 4 parakeets. The same procedure was then used to study frequency difference limens in 6 additional animals. The power spectrum and "constancy of intonation" of the parakeet call were also measured and related to the absolute and differential frequency sensitivity. The mechanism of frequency analysis in the parakeet ear was considered in relation to the present results and to the anatomical and functional differences between the avian and mammalian auditory systems.

Acoustic Stimulation↗

PubMed1999

A behavioral test of presbycusis in the bird auditory system.

Absolute auditory thresholds were determined behaviorally in European starlings (Sturnus vulgaris) between the age of 6 months and up to 13 years using a GO/NOGO procedure. The thresholds that we observed in individual starlings over a time period of 11 years showed no systematic increase over time. When comparing young starlings (age 6 to 12 months) with old starlings (age 8 to 13 years), we discovered no substantial age-related hearing loss. In the frequency range from 0.5 to 4 kHz, the thresholds of old subjects were on average increased by 1.5 to 3 dB. For frequencies of 6 and 8 kHz, the mean threshold increase of old subjects was 6.1 and 4.9 dB, respectively. This demonstrates excellent hearing in subjects that had lived on average more than five times the starlings' demographic life span of 22 months. This result is discussed with respect to the large threshold shift usually found in aging mammals and to differences between the bird and the mammalian auditory system.

Aging↗

PubMed1990

Trimethyltin effects on auditory function and cochlear morphology.

Trimethyltin (TMT) is a neurotoxicant known to alter auditory function. The present study was designed to compare TMT-induced auditory dysfunction using behavioral, electrophysiological, and anatomical techniques. Adult male Long-Evans hooded rats (n = 9-12/group) were acutely exposed to saline, 3, 5, or 7 mg/kg TMT. Auditory thresholds were determined 11 weeks postdosing for 5- and 40-kHz tones using reflex modification of the auditory startle response (ASR). Brainstem auditory evoked response (BAER) thresholds were determined for 5-, 40-, and 80-kHz tonal stimuli 9 weeks postdosing. Cochlear histology was assessed at 13 weeks postdosing. Functional endpoints demonstrated a high-frequency hearing loss. ASR thresholds for 40-kHz tones were elevated 25-35 dB in all dosage groups. BAER thresholds for 40- and 80-kHz tones were elevated 30-50 dB in the 5 and 7 mg/kg groups. Organ of Corti surface preparations revealed a pattern of damage suggesting classical ototoxicity. That is, outer hair cells died preferentially in regions associated with high-frequency hearing, in a dosage-dependent manner from base to apex. These data demonstrate the utility of the ASR and BAER in detecting functional alterations in audition and indicate that TMT-induced high-frequency hearing loss is associated with cochlear damage.

Animals↗

PubMed1997

Age-related changes in the compound action potentials of the eighth nerve in guinea pigs.

The eighth nerve compound action potential (CAP) in 95 guinea pigs was measured using click stimuli to investigate age-related changes in their neural auditory thresholds. The animals were separated into three groups: group A (n = 43, 86 ears; 2-4 months old); group B (n = 29; 58 ears, 13-15 months old); and group C (n = 23; 46 ears, 23-25 months old). With increasing age, a gradual elevation of CAP thresholds was clearly seen among the three groups. The negative peak (N1) latencies of the CAP were prolonged, and the N1 amplitudes of the CAP decreased. There were significant differences in N1 latencies among the three groups and in N1 amplitudes between groups A and B, and between groups A and C. However, the rate of decline of the thresholds as well as the input-output function curves of the CAP varied in some of the oldest animals, suggesting that there were some individual differences in degenerative aging processes of the auditory system.

Acoustic Stimulation↗