[Introduction to the concept the threshold of discrimination of timbre. Preliminary note].
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Auditory Perception↗
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Results for “Auditory Threshold”
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Middle-latency responses to assess objective thresholds in patients with noise-induced hearing losses and Ménière's disease.
In this study 23 patients with noise-induced hearing loss (NIHL) referred for medico-legal evaluation and a group of 18 cases with Ménière's disease were evaluated audiologically using the middle-latency response (MLR). Cross-correlation functions were used to assess precisely MLR thresholds in low and middle frequencies. Cross-correlation data obtained from suprathreshold levels to below threshold levels were compared with the normal limits of parameters found at threshold levels, allowing us to determine the true MLR threshold. Our results revealed that this MLR threshold and visual detection thresholds were different in 18% of both the NIHL and Ménière's disease groups. In this population the true MLR threshold was greater by 5 dB. These findings demonstrated that cross-correlation functions can enhance the sensitivity of the definition of the MLR threshold. True MLR thresholds were compared with subjective pure-tone audiometric (PTA) thresholds at the same frequencies (0.5, 1 and 2 kHz). The true MLR threshold and PTA threshold were in agreement within 10 dB in 91% of the NIHL group and all of the Ménière's disease group. The PTA threshold was greater by 15 dB or more in the remaining NIHL group. If a criterion of 15 dB discrepancy indicates non-organic hearing loss, it can be inferred that 9% of an NIHL population referred for medico-legal evaluation is exaggerating subjective audiometric thresholds.
Adult↗
Evoked otoacoustic emissions in newborn hearing screening.
Evoked otoacoustic emissions (EOEs) were recorded in a group of normally hearing neonates (n = 100 ears) to study the basic properties of EOEs and the parameters influencing them. The results obtained with EOE recordings were compared with those of behavioral screening investigations. The main properties of EOEs in neonates are: 1. EOEs can be recorded in 98% of the tested ears or neonates; 2. there were no statistically significant variations in EOE detection thresholds of neonates between the ages of 1 and 4 days; 3. no statistical difference in the EOE threshold was found between males and females; 4. all EOEs exhibited a broadband spectrum with high-component frequencies; 5. EOEs demonstrating narrowband frequency peaks super-imposed on the broadband component had detection thresholds lower than EOEs without narrowband frequency peaks. EOEs can be used as a screening test. The main clinical interest of this test is to detect the presence (i.e., normal auditory peripheral function) or the absence (i.e., pathological peripheral auditory function) of EOEs in response to a 30-dBHL click stimulation. The results of this study have important applications concerning the possible clinical use of EOEs for screening peripheral auditory dysfunction in neonates.
Audiometry, Evoked Response↗
Paediatric auditory brainstem response and pure-tone audiometry: threshold comparisons. A study of 142 difficult-to-test children.
Auditory brainstem response (ABR) thresholds have been determined in 142 anaesthetized 'difficult-to-test' children. The stimuli employed were 2-kHz tone bursts. Pneumatic otomicroscopy was carried out prior to the ABR assessment in all cases, and diagnostic myringotomy was performed when there was the slightest suspicion of abnormality. Long-term follow-up pure-tone audiograms were obtained in 56 patients. A comparison was made between ABR and pure-tone thresholds in the 2-4 kHz range both in healthy middle ears and in ears having middle ear effusion (MEE) at the time of ABR measurement. A correction factor for prediction of behavioural threshold from the ABR threshold both in healthy and in MEE ears is proposed.
Adolescent↗
Chronic strychnine administration into the cochlea potentiates permanent threshold shift following noise exposure.
To investigate whether elimination of the medial efferent system influences permanent threshold shift following noise exposure, we developed an animal model in which strychnine was chronically delivered into the cochlea via an osmotic pump. Pigmented female guinea pigs were allocated into three groups: group I was treated with strychnine (50 microM, 0.5 microl/h, 14 days) in the left ear and exposed to noise (105 dB SPL broadband, 3 h) 3 weeks after the cessation of the strychnine perfusion; group II received strychnine in the left ear but no noise exposure; group III was treated with Ringer's solution in the left ear and exposed to noise. Animals in group II developed no hearing loss after the strychnine perfusion. The operated ears in group I demonstrated greatest hearing threshold shift 3 h after noise exposure. Hearing recovered during 2 weeks after noise exposure in both operated and non-operated ears in groups I and III. Two weeks after noise exposure, the operated ears in group I showed significantly greater threshold shift at 12, 16, and 20 kHz compared to the operated ears in group III and non-operated ears in groups I and III. These findings suggest that chronic strychnine administration into the cochlea inactivates the medial efferents without changing hearing threshold and that the medial efferents help to protect against permanent threshold shift following noise exposure.
Animals↗
Behavioral thresholds for electrical stimulation applied to auditory brainstem nuclei in cat are altered by injurious and noninjurious sound.
Each of three young-adult female cats with normal hearing received a total of eight permanent electrodes which were implanted bilaterally in cochlear nucleus (CN) and inferior colliculus (IC). Three experiments were performed using behaviorally measured thresholds for electrical stimulation of CN and IC. In Expt. 1, electrical stimulation thresholds (in dB re 1.0 microA) were obtained in the presence of a continuous tone of moderate intensity and in quiet. In comparison with quiet, electrical stimulation thresholds measured during tone were lower by as much as 15 dB (stimulation hypersensitivity). In Expt. 2, a brief exposure to an intense sound produced a temporary threshold shift (TTS) for acoustic stimuli but only produced small changes in electrical stimulation threshold. The acoustic stimuli used in Expts. 1 and 2 were termed noninjurious since no permanent hearing loss was produced. Expt. 3 employed an exposure to a white noise that resulted in a mean permanent threshold shift (PTS) of 34.1 dB for acoustic stimulation. The PTS was accompanied by a mean stimulation hypersensitivity of 9.6 dB. Comparing Expts. 1 and 3, it was shown that the transient hypersensitivity produced by the noninjurious continuous tone correlated strongly with the permanent hypersensitivity that was produced by the PTS. In regard to the origin of stimulation hypersensitivity, the suggestion is made that it is an indication of a physiological change localizable perhaps in the auditory nuclei of the upper brainstem.
Acoustic Stimulation↗
The detection of phantom targets in noise by serotine bats; negative evidence for the coherent receiver.
Using a target simulator three serotine bats, Eptesicus serotinus, were trained to judge whether a phantom target was present or absent. The echolocation sounds emitted by the bats during the detection were intercepted by a microphone, amplified and returned by a loudspeaker as an artificial echo, with a delay of 3.2 ms and a sound level determined by the overall gain and cry amplitude. The cry level of each pulse was measured and the echo level received by the bat was calculated. The target was presented in 50% of the trials and the gain adjusted using conventional up/down procedures. Under these conditions between 40 and 48 dB peSPL were required for 50% detection (Figs. 2, 3). In a subsequent experiment the phantom target was masked with white noise (No) with a spectrum level of -113 dB re. 1 Pa X Hz-1/2. The thresholds were increased by 7-14 dB. Energy density (S) of a single pulse was measured and used to estimate S/No, which ranged from 36-49 dB at threshold. Theoretically the coherent receiver model predicts the ratio between hits and false alarms observed for the bats at a S/No of ca. 1-2 dB. Since the bats require 40-50 dB higher S/No (Fig. 3), this is taken as negative evidence for coherent reception (cross correlation). Furthermore, a strong sensitivity to clutter was found since there seemed to exist a fixed relationship between thresholds and clutter level.
Animals↗
A modification of the Tillman-Olsen method for obtaining the speech reception threshold.
Twenty normal-hearing subjects were tested to determine their speech reception thresholds (SRTs) using the Tillman-Olsen method and a modification of their method requiring no knowledge of the pure-tone audiogram from which to estimate the SRT. Varying amounts of attenuation were added to the line leading to the test earphone to minimize experimenter bias. The data revealed no significant differences between the two methods in either the SRTs themselves or the amount of time required to obtain them. A procedure is therefore advanced for clinicians wishing to measure SRTs without prior knowledge of pure-tone thresholds.
Adult↗
Loudness balance calibration of bone conduction vibrators.
An improved monaural loudness balance method of transferring calibration data among three physically dissimilar bone conduction vibrators was compared with the threshold method. In 19 of 21 possible comparisons, absolute differences between the transfer factors obtained with the two methods were 2.5 dB or less, showing that the monaural loudness balance procedure compares favorably with the threshold method.
Adult↗
Speech-recognition difficulties of the hearing-impaired elderly: the contributions of audibility.
The role that sensorineural hearing loss plays in the speech-recognition difficulties of the hearing-impaired elderly is examined. One approach to this issue was to make between-group comparisons of performance for three groups of subjects: (a) young normal-hearing adults; (b) elderly hearing-impaired adults; and (c) young normal-hearing adults with simulated sensorineural hearing loss equivalent to that of the elderly subjects produced by a spectrally shaped masking noise. Another approach to this issue employed correlational analyses to examine the relation between audibility and speech recognition within the group of elderly hearing-impaired subjects. An additional approach was pursued in which an acoustical index incorporating adjustments for threshold elevation was used to examine the role audibility played in the speech-recognition performance of the hearing-impaired elderly. A wide range of listening conditions was sampled in this experiment. The conclusion was that the primary determiner of speech-recognition performance in the elderly hearing-impaired subjects was their threshold elevation.
Adult↗
Effects of varying unilateral conductive hearing losses on speech-in-noise discrimination: an experimental study with implications for surgical correction.
HYPOTHESIS: Unilateral conductive hearing loss (HL) causes measurable disability in realistic hearing environments. The benefits of improving this loss depend both on the absolute level of final hearing and on hearing asymmetry. BACKGROUND: Surgical success is often measured by the degree of change in the air-bone gap or in the air thresholds. The Glasgow Benefit Plot and the Belfast Rule of Thumb suggest that a given hearing gain will be of greater benefit if the postoperative thresholds in the worse ear are a <30-dB HL or within 15 dB of the contralateral ear. This assertion has important surgical implications, but few audiometric data supporting it currently exist. METHODS: Speech-in-noise sound-field scores were measured in 16 normal volunteers at three presentation levels at two signal-to-noise ratios (SNRs). Two levels of unilateral conductive HL were simulated with earplugs, averaging 25-and 43-dB HL, respectively, and the effect on speech-in-noise scores was measured and analyzed. RESULTS: Unilateral conductive HL is a disadvantage at lower sound intensities and low SNRs, but it can be compensated for by increasing volume or SNR. The benefits of improving unilateral conductive HL are greater if the final asymmetry is <25 dB and the final hearing threshold is <25 dB. CONCLUSIONS: Unilateral conductive HL is a significant disadvantage at low SNRs or presentation volumes. The benefits of surgery to improve HL depend not only on the degree of hearing improvement but also on the final hearing threshold in both ears.
Adult↗
Interaural level differences and the level-meter model.
The interaural level difference (ILD) plays a significant role in sound localization. However, the definition of ILD for noise is open to some interpretation because it is not obvious how to deal with the inevitable level fluctuations. In this article, the ILD is interpreted as an energylike (time-integrated) measure of stimulus level, independent of other stimulus details-particularly interaural correlation. This concept is called the "level-meter model." The model was tested by measuring human ILD thresholds for noise stimuli that were interaurally correlated, or anticorrelated, or uncorrelated. An additional test (not involving lateralization) measured the threshold for level discrimination based on loudness. According to the level-meter model, all four thresholds should be the same. The experimental results showed that the predictions of the level-meter model held good to within about half a dB, although thresholds for level discrimination were systematically higher than ILDs. Among the ILDs themselves, thresholds were slightly higher for uncorrelated noise. The latter result could be explained by replacing the level-meter model with a loudness-meter model, incorporating temporal integration. The same model accounted for the bandwidth dependence of the threshold.
Adult↗
Effect of signal frequency and masker level on the frequency regions responsible for the overshoot effect.
Two experiments investigated the relative influence of components close to and remote from the signal frequency (fs) on the overshoot effect. Overshoot was defined as the difference in threshold between a signal presented 4 ms after, and that for one presented 300 ms after, the onset of a 350-ms masker. Experiment 1 measured the overshoot effect using both wideband and narrow-band maskers (centered on fs), at two signal frequencies and three masker levels. Experiment 2 used a masker consisting of a "middle band" (MB, centered on fs) and two flanking bands (FBs, which, when combined with the MB, produced a flat wideband spectrum). The masker was continuous except for a 300-ms interval just prior to the signal, during which either all three bands, the MB alone, or the FBs alone were turned off. The results of both experiments showed that the overshoot effect was usually determined by off-frequency components. However, the on-frequency components played a substantial role when signal-to-noise ratios (SNRs) at threshold were unusually high, such as at fs = 6500 Hz and intermediate masker levels. It is suggested that two different mechanisms contribute to the overshoot effect: an off-frequency mechanism which operates at all fs and masker levels, and an on-frequency mechanism which contributes to the overshoot effect only at high-threshold SNRs.
Attention↗
Maximum-likelihood yes-no procedure for gap detection: effect of track length.
A maximum-likelihood yes-no procedure was used to measure minimum detectable gaps (MDGs) at 1 and 4 kHz using two track lengths (15 and 30 trials). Results from 11 normal listeners show no difference between MDGs for the two track lengths, and variability of the MDGs did not differ significantly for the track lengths. Results from simulations indicate that the variability of MDGs from real listeners is considerably larger than that imposed by the psychophysical procedure. Additional simulations show that random variability of listeners' response criterion is a compelling explanation for the excess variability. These findings indicate that changes in a listener's threshold over time impose a lower bound on the variability obtainable with a yes-no procedure. They imply that increasing the number of trials in a track, beyond the minimum number required to obtain a stable threshold estimate, offers little or no advantage for the test-retest reliability of a clinical threshold measurement.
Adult↗
[What average hearing gains can be expected at present with children wearing hearing aids?].
The narrow band noise-audiometric free-field hearing threshold of hearing aids encloses at least some of the essential part of the acoustic language field even in marked unisensory infant hearing impairment. Thus auditive promotion is to be preferred even in "deaf" children compared to optic-tactile aids. This has an advantage for language development and also has consequences for the method of training. Statistical evaluation of the pure tone and narrow band noise-audiometric data allows conclusions to be drawn about the quality of hearing aids adjustment and especially about the importance of the medium pure tone-audiometric hearing thresholds limit at 70-75 dB.
Audiometry↗
[Stapedius reflex. 1. Stapedius reflex threshold and recruitment].
UNLABELLED: The stapedius reflex threshold and pure tone threshold of 173 patients with normal hearing and cochlear disorders were examined (using Madsen ZO 73 equipment). CONCLUSIONS: 1. The aetiology of the cochlear hearing disorders does not influence the stapedial reflex threshold. 2. A linear regression between hearing loss and threshold difference was found in cochlear hearing disorders. 3. No correlation could be found between individual pure tone threshold and stapedial reflex threshold.
Adolescent↗
[The reaction time as a source of error in threshold audiometry (author's transl)].
An investigation of reaction times at the threshold of hearing is described. 96 subjects were classified into two groups of sensorineural hearing loss utilizing Types I and II Bekesy audiometry, and compared with one normal group as control. The results show that reaction times are largely unaffected by the type of hearing loss and test frequency. Increasing age, however, may result in increasing reaction times. These results and possible sources of error are discussed as effecting an exact threshold audiometry.
Adult↗
Tinnitus as an early indicator of permanent hearing loss. A 15 year longitudinal study of noise exposed workers.
A retrospective study was designed to evaluate tinnitus (ringing or other sounds in the ears or head) as a potential early indicator of permanent hearing loss in a population of noise exposed workers. Data were examined from 91 male employees working in environments with noise levels ranging from 8 hour time weighted averages of 85 to 101 dBA over a period of 15 years. Results of annual audiometric testing were obtained as part of an ongoing hearing conservation program conducted since 1971 by ESCO Corporation, a steel foundry located in the Portland, Oregon metropolitan area. Results indicate the prevalence of tinnitus increases more than two and one half times for workers experiencing maximum threshold shifts > or = 15 decibels in hearing level (dBHL). Results also provide evidence that reports of tinnitus at the time of annual audiometric testing may be useful in identifying workers at greater risk for developing significant shifts in hearing thresholds.
Adolescent↗