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PubMed1981

Speech recognition performance at loudness discomfort level.

The purpose of this experiment was to determine the relationship between the loudness discomfort level (LDL) and maximum speech recognition performance for listeners with sensorineural hearing loss. Performance-intensity functions were obtained for 30 listeners with mild to moderate sensorineural hearing impairment at five speech levels from -18 to +4 dB re: the LDL. Recognition scores were obtained for three speech materials. For all speech materials, recognition scores at levels below the LDL were equivalent to or higher than scores obtained at and above the LDL. These results support the contention that the LDL represents a sound pressure level above which no improvement in speech recognition occurs, and thus, might reasonably be used as the appropriate level for the saturation sound pressure level of a hearing aid.

Amplifiers, Electronic↗
PubMed1982

Hearing aid selection by brainstem audiometry.

Hearing aid selection and adjustment by means of brainstem audiometry was tested in 29 hearing impaired children. A projection procedure is introduced which employs normal and pathological intensity-amplitude functions. This method enables determination of some basic properties of appropriate hearing aids, such as average gain, type of compression, compression factor and onset level. Hearing aid evaluation is discussed for two examples of conductive and sensorineural impairment.

Adult↗
PubMed1984

Simultaneous recording of auditory evoked potentials. Relationships among the fast, middle and long latency components.

The whole pattern of the fast, middle and long latency auditory evoked potentials (AEP) was recorded simultaneously from the scalp surface of 13 normal-hearing adults. The individual responses were displayed on a nonlinear time axis in order to improve identification of the components. Stimulation consisted of 2048 unfiltered clicks, delivered monaurally at 80, 60, 40 dB HL with an ISI of 750 ms. Changes in mean latency and amplitude of each AEP component were statistically evaluated in relation to intensity and electrode montage (vertex-mastoid ipsi- and contralateral to the stimulated ear). The latencies of fast components I-VI and the slow P1 increase significantly with declining stimulus intensity. The amplitudes of the fast, I, II, III, V and the slow P1-N1, P2-N2 decrease significantly with intensity. As regards differences due to the electrode montage the contralateral recording causes significant changes in latency of the fast potentials up to wave IV, and changes in amplitude of the fast up to wave V, and of the slow P1-N1 and P2-N2. Therefore, as their latency and amplitude seem to be less closely related to the stimulus and electrode placement, the middle components behave differently, compared with the preceding and following components. Based on parametric comparisons of potentials ranging widely in latency, but each one evoked by an equal sensory input, this kind of AEP evaluation may be useful both for neurophysiological and clinical studies of the whole auditory pathway function.

Adult↗
PubMed1984

Middle components of the auditory evoked response in young children.

The purpose of this study was to ascertain whether the middle components of the auditory evoked response could be obtained consistently from normal young children during sleep. The wave pattern of the response was unstable and was not reproducible in sleeping children. Comparing the detectability of each peak in waking children with that of each peak in sleeping children, there was little difference in the detectabilty of the Po peak between the two test conditions, and the Na peak was only about 10% lower in sleeping subjects than in waking ones. However, a considerable decrease in the detectability of the Pa peak was found during sleep. Later peaks, such as the Nb and Pb peaks, which are usually elicited in waking adults, could scarcely be found in children, either in the sleeping or in the wakeful state. In this study, no clear difference of detectability in each peak could be demonstrated between the two filter conditions. From these results, it is concluded that the middle components of the electroencephalic response in sleep differ from those in the waking state, especially in children. Moreover, it seems that the decrease in the appearance of the response during sleep may be related to the depth of sleep. Po-Na may be the most suitable index for electric response audiometry in young children.

Auditory Threshold↗
PubMed1985

The effect of type of hearing loss on hearing aid use.

This study examined the effect of type of loss and reduced PB discrimination on hours of daily hearing aid wear. Patient data were entered in one of four matrices designed to permit examination of one variable while balancing the effects of other variables. When the influences of amount of hearing loss, age, hearing aid experience, and employment status were balanced, no evidence was found that type or shape of loss influenced the number of hours of daily hearing aid use. When the data for each type/shape of loss were pooled without regard to amount of loss, age, aid experience, and employment status, hours of reported wear were least for those with normal hearing in the better ear (8 hours) and most for those with conductive components (15.8 hours). Since patients with conductive components had the largest hearing losses, it was concluded that hours of wear are influenced primarily by amount, not type of loss. Discrimination scores were examined within the same balanced design. Although PB max scores for patients with conductive components were systematically higher than scores for patients with sensorineural losses, the reported wear times were essentially the same. Previous findings that sensorineural hearing loss and reduced speech discrimination adversely influenced hearing aid wear were attributed to differences in amount of loss and other intervening psycho-socio-vocational variables.

Aged↗
PubMed1985

The effect of sleep on the auditory brainstem response (ABR) and the middle latency response (MLR).

The ABR and the MLR were measured without interruption in 4 subjects during a whole night of natural sleep and compared with the awake responses. The conventional EEG activity was monitored during the whole procedure, which permitted a precise rating of the sleep stage during each recording period. Only minor changes were found in the latencies for the ABR during sleep. The MLR responses showed quite dramatic changes in morphology and latencies. Our results appear to indicate that the 40/sec stimulus presentation mode of the MLR will not be very effective during sleep due to the pronounced latency shifts of the different peaks in the MLR. The 40/sec response is based on an inter-peak latency of 25 msec. If this presumption is not fulfilled the different waves in the 40/sec response will not be superimposed and consequently enhanced in the averaging procedure.

Acoustic Stimulation↗
PubMed1985

The 40-Hz event-related potential as a measure of auditory sensitivity in normals.

Estimates of behavioral threshold using the 40-Hz Event-Related Potential (ERP) were obtained on sixteen normal subjects at frequencies of 500, 1000, 2000, and 4000 Hz, and compared with behavioral thresholds for the same stimuli. The mean differences were within 10 dB at the three lowest frequencies. The mean difference at 4000 Hz was 16 dB. Peak amplitude of the response did not vary significantly either with signal amplitude or test frequency, but the latency of the response varied significantly with frequency. Factors which may affect the reliability and validity of the 40-Hz ERP are discussed.

Adult↗
PubMed1987

The objective estimation of loudness discomfort level using auditory brainstem evoked responses.

The loudness discomfort level (LDL) is of importance in the fitting of hearing aids, but very young children are unable to provide a subjective judgement of LDL. Therefore the relationship between Jewett wave V latency and subjective loudness was investigated to ascertain if objective estimation of LDL is possible. ABR recordings were taken from 8 normally hearing subjects at the stimulus intensity corresponding to their LDL and at stimulus levels from 10 to 30 dB below this. The wave V latency/intensity function did not correlate well with the LDL. However, the slope of this function did correlate to a high degree and a predictive model of LDL was derived. Identical measurements were then taken from a sample of 12 cochlear-impaired subjects with a range of audiometric profiles. Their subjective LDLs could be predicted from the wave V latency function to an accuracy of +/- 5 dB, using the model derived from the normally-hearing subjects. This model appeared to be equally valid for all the degrees and profiles of hearing loss included in the sample and showed a closer relationship to LDL than did absolute wave V latency or estimates derived from the acoustic reflex.

Adult↗
PubMed1987

Auditory brainstem responses to single-slope stimuli. The influence of steepness and polarity.

Click polarity has little influence on brainstem potentials. We applied an auditory stimulus similar to a step function generated in a closed acoustic system. The influence of stimulus onset steepness (comprising rise time and intensity) on wave V latency and amplitude was investigated. A remarkable latency prolongation was observed for condensation (C) compared with rarefaction (R), if a sharp bend at the foot of the slope was avoided. The C latency lag was nearly the amount of rise time. The effect can be explained by cochlear travel time. Wave V amplitude for R slopes was significantly enhanced. At high intensity and short rise time, it reached twice the values found with C slopes, or with clicks of either polarity. Although the explanations found are not yet satisfactory, a clinical application in cochlear diagnosis is predictable.

Adult↗
PubMed1989

Clinical methods for the objective estimation of loudness discomfort level (LDL) using auditory brainstem responses in patients.

Our previous work showed that the slope of the JV latency/intensity function can be used to estimate the loudness discomfort level (LDL). In this study, the previous work was repeated using normal subjects and patients whose LDL was unknown at the time of test. The results showed that the original model still applied. Further measures were taken to evaluate clinical methods of applying this technique. Four basic approaches were used, a 'correction factor' model and a 'curve-fitting' model and these were applied to data obtained from measurements taken in both 5 dB and 10 dB increments. The results showed that the 'correction factor' models were better than the 'curve-fit' approach. The prediction of LDL based upon the 5 dB increment data gave the greater accuracy but the 10 dB increment data gave predictions that were sufficiently accurate for clinical use (95% confidence limits of +/- 8 dB). Thus this ABR estimator has wide application and good accuracy in estimating subjective LDL. A clinical protocol for applying this technique is described.

Adolescent↗
PubMed1991

A proposal for the measurement of the level of fluctuating background noise used in audiology.

Disturbances of communication in noisy environments may be identified sooner in patients with sensorineural hearing loss when speech audiometry is performed using fluctuating rather than stationary background noises. In the present study, the factors determining the loudness of fluctuating noises were examined using psychoacoustical procedures. The results indicated that loudness of fluctuating noises was best represented by the same percentile loudness N15 or percentile level L15. This is the value that is reached or exceeded in 15% of the analysed measurement time. The percentile level L15 or the percentile loudness N15 may be used to measure the level of noises with identical spectra. However, subjective loudness is approximated only by the percentile loudness N15 if the stationary and the fluctuating noises are spectrally different.

Adult↗
PubMed1995

Loudness discomfort levels and saturation levels in hearing aids prescribed for young persons.

Hearing aids were re-evaluated for 18 persons aged 11-16 years. Since these aids were fitted mainly using an informal test of aided loudness discomfort, the saturation levels were re-evaluated with a new magnitude-estimation procedure for measuring unaided and aided loudness discomfort levels. Sixteen subjects had used hearing aids capable of producing uncomfortably loud warble tones. New hearing aids were fitted according to the new loudness discomfort data and the NAL recommendation for insertion gain. When forced to choose between the previously prescribed hearing aids and the new aids after three weeks of real life comparison, most subjects preferred the new instruments, but three persons finally decided to wear hearing aids with saturation levels exceeding their loudness discomfort levels. The magnitude estimation procedure was found to be clinically feasible, although problems with the instruction caused uncertainty in some cases. Measured loudness discomfort levels increased 5-10 dB between test and retest sessions.

Adolescent↗
PubMed1996

Loudness ratio production by cochlear implantees using the spectral maxima sound processor.

The loudness growth characteristics of five users of the Mini System 22 implant and the Spectral Maxima Sound Processor were measured and compared with those of five normally hearing subjects. The main objective was to evaluate the suitability of the function employed in the sound processor that converts acoustic input levels of electrical stimulation. The method of loudness ratio production was used. The average result of the normally hearing subjects for halving and doubling loudness was 10.8 dB. The results of three of the implantees were comparable with those of the normally hearing subjects (average 8.83 dB), while those of the remaining subjects were quantitatively and qualitatively different. Investigation showed that altering the amplitude conversion function in the sound processor would not make the results of these two implantees more like those of the other subjects. However, it is possible that their responses were affected by the limited input dynamic range of the sound processor.

Adult↗
PubMed1998

Are clinical measurements of uncomfortable loudness levels a valid indicator of real-world auditory discomfort?

A recent study revealed that most patients were wearing National Health Service hearing aids that were capable of exceeding their uncomfortable loudness level (ULL) measured clinically (Munro et al., 1996). However, there is little evidence to show that these clinical measurements are a valid indicator of real-world auditory discomfort. The aim of this study was to investigate the relationship between ULL and real-world discomfort. The study involved 20 adult subjects, aged 41-92 years, who had been fitted monaurally with an NHS hearing aid. ULLs were measured using a probe-tube microphone situated close to the eardrum. Individual real ear to coupler differences were added to the SSPL90 in order to predict the maximum power output (MPO) of the hearing aid at the eardrum. Subjects completed a questionnaire designed to rate the loudness of different environmental sounds. The results show that the more the MPO value exceeded the ULL value, the more likely it was that the subjects reported loudness tolerance problems to environmental sounds of long duration. There was a statistically significant correlation between the ULL and discomfort ratings for sounds of longer duration, such as traffic and wind noise; but not for shorter-duration sounds, such as door banging. Subjects did not express real-world auditory discomfort when the MPO value matched the ULL value. These findings support the argument for setting hearing-aid MPO close to ULL.

Adult↗
PubMed1998

Use of a loudness model for hearing-aid fitting. I. Linear hearing aids.

A model for predicting loudness for people with cochlear hearing loss is applied to the problem of prescribing the frequency-gain characteristic of a linear hearing aid. It is argued that a reasonable goal is to make all frequency bands of speech equally loud while achieving a comfortable overall loudness; this can maximize the proportion of the speech spectrum that is above the absolute threshold for a given loudness. In terms of the model this means that the specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band), and the overall loudness should be similar to that evoked in a normal listener by 65 dB speech (about 23 sones). The model is used to develop a new formula - the 'Cambridge formula' - for prescribing insertion gain from audiometric thresholds. It is shown that, for a fixed overall loudness of 23 sones, the Cambridge formula leads to a higher calculated articulation index than three other commonly used prescriptive methods: NAL(R), FIG6 and DSL.

Auditory Threshold↗
PubMed1979

Critical bandwidth in loudness summation in sensorineural hearing loss.

Critical band estimation was performed in thirty-three patients with sensorineural hearing loss by the method of loudness summation, using noise bands centred around 1 kHZ. In 17 patients the hearing loss was of hereditary origin, in 16 patients of various, mostly unknown, origin. The normal loudness difference between broad band noise and narrow band noise decreased with increasing hearing loss, most pronounced in recruiting ears. Judged individually, 1/3 of the patients appeared to have a widened critical band, but several biases appeared to be responsible for these results. The pooled data indicated a normal critical band, both in patients with hearing losses less than 50 dB HL and in patients with hearing losses greater than or equal to 50 dB HL. Based on this finding, the validity of the critical band as a measure of the frequency selectivity of the ear is discussed and a theory is proposed for the anatomical and functional correlate of the critical band in loudness summation.

Adult↗
PubMed1979

Investigation of the relationship between adaptation measured binaurally and monaurally.

Recently it has been demonstrated that auditory adaptation can be measured with a monaural technique (Weiler and Friedman, 1973; Weiler and Gross, 1976; Feaster and Weiler, 1975). Because the magnitude of adaptation measured monaurally was nearly identical to that measured binaurally in other experiments, it was assumed that they measured the same phenomenon or phenomena. In the present study the same group of subjects were tested for magnitude of adaptation both monaurally and binaurally. The means were 11.75 dB and 12.17 dB, respectively (N=13). Depsite nearly identical means for the present conditions there was no significant correlation (r=+.27) between the magnitude of adaptation measured under the two conditions. Except for the possibility that individual differences in the ability to do monaural versus binaural tasks may have obscured individual similarities in adaptation, the only other explanation the authors can suggest is that the two techniques measure different aspects of loudness adaptation.

Adult↗
PubMed1979

Monaural balances and loudness coding during auditory adaptation.

A monaural simultaneous balance technique was used to compare amounts of adaptation for two conditions: (1) with the test intensity equal to the adapting intensity, and (2) with the test intensity +10 dB above the adapting intensity. Previous findings (Weiler and Hood, 1977) showed a decline in measured adaptation for the second condition using simultaneous binaural balances. That this was not the case for the monaural balances investigated in this study may indicate different adaptation-induced auditory changes are being measured monaurally vs. binaurally.

Adult↗