A hearing conservation programme for small industries in a Swedish county.
Explore the source record for details and available documents.
Audiometry↗
Biomedical subjects
S Arlinger
Publications and source records attributed to S Arlinger.
Drill-generated noise levels in ear surgery.
The noise levels in the cochlea when a drill is used in the mastoid process have been calculated from vibration measurements on intact skulls of human cadavers and temporal bones. The results lend support to the conclusion that, in ear surgery the ipsilateral cochlea is exposed to noise levels of about 100 dB and the contralateral cochlea to levels 5-10 dB lower every time the drill is used. This noise trauma may account for some of the high-tone sensorineural hearing losses after tympanoplasty described by other authors.
Ear↗
Variables affecting the drill-generated noise levels in ear surgery.
The manner in which the variables rotation speed, type of burr, burr size and site of drilling influence bone-conducted, drill-generated noise levels in ear surgery, has been investigated. From the results obtained, the following conclusions can be drawn. 1. The noise levels were primarily influenced by the size of the burr. The 6 mm cutting burrs gave a noise level of 88-108 dB, the use of a 4 mm one resulted in a reduction of 1-6 dB and the use of a 2 mm one, 5-16 dB. The mean noise levels of the diamond burrs were 5-11 dB lower than the mean noise levels of the cutting ones. 2. Variations in rotation speed had only a slight influence on the noise levels produced (0-5 dB). 3. Three different types of cutting burr were tested. All gave noise levels of about the same order of magnitude. 4. The noise levels around the cochlea were only slightly influenced by the localization of the drilling within the ear (less than 1.8 dB). 5. Drill-induced noise levels in ear surgery cannot be reduced to any great extent. Possible noise traumas to the inner ear can only be avoided by minimizing the duration of drilling and thus, the duration of harmful noise exposure to the cochlea.
Ear↗
Electrocochleography with bone-conducted stimulation. A comparative study of different methods of stimulation.
Due to the shortcomings of the conventional bone vibrators available at the present, electrocochleography with bone conducted acoustic stimulation has not found any clinical application despite the fact that methods for the procedure have been developed for some time. The most striking deficiencies of these vibrators are their unsatisfactory stimulus intensities and their lack of frequency specificity due to distortion. Driven by an a.c. signal, a piezoceramic accelerometer (A21T, D. J. Birchall Ltd.) was found to meet the requirements of clinical use giving satisfactory stimulus intensities with a minimum of distortion when attached to the mastoid process by means of a modified bone screw.
Acoustic Stimulation↗
Auditory processing of frequency ramps.
Linear frequency ramps of a continuous pure tone have been used as stimuli, and behavioral thresholds for frequency change (DLF) as well as the slow cortical potentials evoked by such ramps have been studied on listeners with normal hearing and with various types of hearing losses. A group with cochlear hearing losses showed elevated DLFs as compared to the normal group by an average factor of 3, independent of ramp duration (10-500 ms). Corresponding to this finding, the slow evoked cortical potentials of the cochlear group had longer N1 latencies at small frequency ramps than those of the normal group. However, at larger ramps, this difference disappeared and turned into the opposite relation at the largest ramps. This result has been verified by a psychoacoustical method, indicating the existence of 'recruitment of pitch change'. In a number of subjects with retrocochlear lesions, the evoked cortical responses to frequency ramps were significantly different from those of the normal group as well as of the group with cochlear lesions.
Acoustic Stimulation↗
Speech recognition and just-follow-conversation tasks for normal-hearing and hearing-impaired listeners with different maskers.
Speech recognition (SRT) and just-follow-conversation (JFC) tasks were performed by normal-hearing and hearing-impaired listeners matched for age and sex using three masking backgrounds: speech spectrum random noise, continuous forward speech and reversed speech. In the SRT task, the signal-to-noise (S/N) ratio for 50% correctly repeated words of short, 5-word, low-redundancy sentences was determined. In the JFC task, the listener adjusted the speech level until he felt he could just understand what was being said. The listeners needed a higher S/N ratio for the JFC task than for the SRT task. The speech maskers gave less masking than the random noise. No difference between forward and reversed speech was observed. The hearing-impaired listeners needed a higher S/N ratio than the normal-hearing subjects. Correlations between results obtained with the SRT and the JFC techniques were significant with speech but not with random noise as masker. The highest correlations between pure-tone hearing thresholds at different frequencies and results in the SRT and JFC tests were seen at 0.5 and 1 kHz.
Adult↗
Reproducibility of the electric response components in clinical electrocochleography.
The reproducibility of transtympanic electrocochleographic components was investigated in normal-hearing subjects and in patients with Menière's disease. The electric responses to short clicks and long tone bursts were studied using repeated stimuli within the same test (intratest), and after replacement of all electrodes (intertest). The parameters of the response to clicks, such as the SP/AP (summating potential/action potential) ratio and the width of the complex as well as the amplitudes of the response to clicks presented at fast repetition rate, were analyzed. Absolute amplitudes of the SP were measured using long tone bursts of 4, 2 and 1 kHz. It was found that the intratest reproducibility of the responses was good for all the parameters. The intertest responses showed a larger variability, particularly when long bursts were used. Parameters obtained from hydroptic ears, which could be considered mainly representative for the SP, showed the largest variability of the responses. The effect of replacement of the electrodes amounted to less than 35% of the total intertest variability which would indicate that replacement of the electrodes did not significantly influence the recordings obtained at different measurement occasions in the same patient. The upper normal limit value indicating changes which could be contributed to biological fluctuations and the method of measurements were calculated for each response parameter. Changes exceeding these values could thus be attributed to a real change in the electric cochlear potentials, at the 95% confidence level.
Acoustic Impedance Tests↗
Evaluation of a cognitive test battery in young and elderly normal-hearing and hearing-impaired persons.
A cognitive test battery sensitive to processes important for speech understanding was developed and investigated. Test stimuli are presented as text or in an auditory or audiovisual modality. The tests investigate phonologic processing and verbal information processing. Four subject groups, young/elderly with normal-hearing and young/elderly with hearing impairment, each including 12 subjects, participated in the study. The only significant effect in the text modality was an age effect in the speed of performance, seen also in the auditory and audiovisual modalities. In the auditory and audiovisual modalities, the effects of hearing status and modality were seen in accuracy parameters. Interactions between hearing status and modality, both in accuracy and in reaction times, show that hearing-impaired subjects have difficulties without visual cues. Performing the test battery in noise made the tasks more difficult, especially in the auditory modality and for the elderly, affecting both accuracy and speed. Test-retest measurements showed learning effects and a modality-dependent variability. The test battery has proven useful in assessing the relative contribution of different input signals and the effects of age, hearing impairment, and visual contribution on functions important for speech processing.
Adult↗
Threshold extrapolation for N1-latencies in auditory evoked responses.
Explore the source record for details and available documents.
Acoustic Stimulation↗
Reference data for evaluation of occupationally noise-induced hearing loss.
Relevant reference data are required in order to determine the effect from occupational noise exposure on hearing. Pure-tone averages (PTA) of hearing threshold levels simplify the evaluation for audiometric frequencies typically affected by noise. The present study provides reference data of high frequency (HF) PTA over 3, 4 and 6 kHz for a general adult population, aged from 20 to 79 years, not exposed to hazardous occupational noise. The results are presented as statistical distributions of HF PTA values as functions of age, and as prevalence of different degree of HF PTA in the age groups 20-29, 30-39, 40-49, 50-59, 60-69 and 70-79 years.
Adult↗