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Biomedical subjects

M E Lutman

Publications and source records attributed to M E Lutman.

At least 55 records · Page 3Linked to original sources
PubMed1992

Apportionment of noise-induced hearing disability and its prognosis in a medicolegal context: a modelling study.

Apportionment of liability for noise-induced hearing loss is required in medicolegal work when two or more separate instances of noise exposure have occurred. In general there are insufficient audiometric records to determine how much hearing loss was caused by each noise exposure, and hence there is insufficient information on which to base apportionment of liability. Apportionment must then be based on a theoretical understanding of the way in which hearing loss is related to patterns of noise exposure and how the increased hearing threshold levels lead to greater disability. A model is developed which combines existing models of the relationship of hearing impairment to noise exposure and age, and the relationship of hearing disability to impairment. The model is evaluated for a wide range of notional patterns of noise exposure, leading to a simple equation which predicts the relative attribution of disability to previous noise exposures sufficiently accurately for the purposes of apportionment. The model also shows that disability due to noise exposure generally increases slightly with increasing age even after noise exposure has ceased. Thus the difference in disability between a person exposed to noise and a noise-free control of the same age and sex can be expected to increase somewhat as the subject and control grow older. However, the magnitude of this effect, often termed prognosis, is shown to be small and can be assumed to be zero in practice.

Age Factors↗
PubMed1992

Consequences of the change to standards for air-conduction hearing levels. A cautionary note.

The issue of BS 2497 Parts 5 and 6 in 1988 brought British Standards into line with the latest revisions to ISO 389. As a consequence, many audiometers that were previously calibrated using a 9-A coupler will now have to be calibrated with an artificial ear. Whilst this may appear to be a seemless change involving merely alterations to measurement apparatus, this technical note illustrates for two earphone types that it entails a shift in the Hearing Level standard by a maximum of 3 dB at 2 kHz. This has ramifications for longitudinal studies of hearing and for monitoring of hearing threshold levels in persons exposed to noise.

Audiometry↗
PubMed1991

The limited accuracy of bone-conduction audiometry: its significance in medicolegal assessments.

Accurate bone-conduction testing with masking is always difficult, but for clinical purposes limited accuracy suffices. However, when assessing claimants for compensation, extreme care is needed since even small apparent air-bone gaps are sometimes translated into financial abatement. This paper sets out the stringent test conditions required to achieve adequate precision. It also indicates the inaccuracies inherent in such tests, and recommends procedures for interpreting the significance of bone-conduction thresholds.

Audiometry↗
PubMed1991

Frequency resolution as a function of hearing threshold level and age.

Frequency resolution ability was measured using a psychoacoustical tuning curve (PTC) or a notch-noise technique in two population samples. The first sample incorporated 1764 subjects with various degrees of sensorineural hearing impairment and ranging in age from 17-80 years. The second sample included 240 subjects aged between 50 and 75 years, carefully balanced in terms of impairment and age to avoid confounding between these two variables. In both samples, frequency resolution ability declined with increasing hearing threshold level (HTL), as measured by either method. In a subsample tested with both methods, the correlation between the two was only modest. After accounting for HTL, there was a minor dependence of frequency resolution on age, older subjects having poorer frequency resolution once HTL had been accounted for. No addition to the explained variance was achieved by taking sex, occupational group, or audiogram slope into account. Despite the documented reproducibility of the measures, much of the variance in the frequency resolution measurements remained unrelated to HTL or age.

Adolescent↗
PubMed1991

Comparative study of four noise spectra as potential tinnitus maskers.

Ten experienced tinnitus-masker uses compared four widely different noise bands as potential maskers in a laboratory environment. No reliable individual preferences could be found, and most of the noises were acceptable to most of the subjects. A wide-band noise was marginally most frequently preferred. In this sample, there was no indication that individual tailoring of the frequency spectra of tinnitus maskers is required to achieve acceptable masking. Subjects also underwent tests of hearing, tinnitus matching and tinnitus masking. Most subjects chose noise levels for therapeutic masking that only partially masked their tinnitus. This suggests prescription or trial of tinnitus maskers even for patients who have high minimal masking levels.

Audiometry↗
PubMed1990

Occupational noise and demographic factors in hearing.

The effects of age, sex, socioeconomic background and noise exposure on hearing were examined in a population sample. Subjects, aged between 17 and 80 years, were selected from the electoral register using a stratified random sampling technique based on age and reported hearing difficulty. Exposure to occupational, social and gunfire noises was estimated retrospectively from a structured interview. Analysis of the audiograms of 2,162 subjects free from any material conductive impairment led to a simple model requiring only first-order factors of age, occupational group (manual or non-manual) and occupational noise exposure, but with parameters different for the two sexes. These models accounted for up to 58% of the variance in hearing threshold level (HTL), depending on frequency. It was not possible to separate out gunfire noise exposure as a factor because of a confounding effect of age. For females there was no significant effect of noise exposure, possibly owing to small numbers of noise-exposed females. The dependence of HTL on age agreed well with published literature, particularly for males. For males, noise exposure was associated with a modest increase in HTL, mainly between 3 and 6 kHz. The model was consistent with reported HTLs for males with equivalent noise exposure.

Adult↗
PubMed1990

Degradations in frequency and temporal resolution with age and their impact on speech identification.

Measures of frequency resolution were obtained in two population samples. The first sample comprised 1764 subjects with various degrees of sensorineural hearing impairment aged from 17 to 80 years. The second sample included 229 subjects with ages between 50 and 75 years, balanced to avoid confounding the effects of impairment and age. Subjects in the second sample were also assessed using a gap-detection measure of temporal resolution and a test of speech identification using sentences in noise. In both samples, frequency resolution ability declined progressively with increasing hearing threshold level (HTL). After accounting for the effects of HTL, there was a minor dependence of frequency resolution on age, older subjects having poorer frequency resolution. Temporal resolution deteriorated with HTL but not with age. The speech identification scores could be predicted from HTL at 2 and 8 kHz and age. Frequency resolution was not a factor. Temporal resolution was only a factor when subjects with extremely poor temporal resolution were included.

Aged↗
PubMed1990

Hearing disability in the elderly.

Hearing disability increases with hearing impairment and impairment increases with age, especially for persons over the age of 50 years. Older subjects also appear to display an excess disability, additional to that expected from impairment. This paper quantifies the excess disability and its dependence on sex and socio-economic factors. A variety of performance tests and a self-administered questionnaire concerning disability and handicap were conducted in 2,466 subjects aged between 17 and 80 years, although the actual tests varied amongst subjects. Performance tests included words in quiet and sentences in noise. Results showed the expected systematic increase in all disability measures with increasing hearing threshold level. For the performance measures, there was excess disability with age, but for self-report the disability was under-rated by older subjects with mild impairments. Females generally performed better than males and non-manual workers better than manual workers for a given hearing threshold level. There was only a low correlation between the results of performance tests and self-report.

Aged↗
PubMed1990

Quality estimation of click-evoked oto-acoustic emissions.

The Fsp statistic used by Elberling & Don (1984) as a quality estimator for averaged ABR recordings has been applied to averaged click-evoked oto-acoustic emissions. This statistic is akin to signal-to-noise ratio. The sampling distribution of Fsp under the null hypothesis that no signal is present has been determined by using no-stimulus trials. A determination by multiple replications in three normally-hearing adults demonstrated significant inter-subject variation, leading to a larger experiment in 58 children. From the latter experiment, the sampling distribution across subjects allowed the setting of a criterion value for Fsp of 2.0 which was only exceeded on 1% of trials. Thus, values above this criterion would indicate the presence of a signal in the average with a probability of Type I error below 1%. When two consecutive average both exceeded an Fsp of 1.6 the probability of Type I error was also below 1%.

Adult↗
PubMed1989

Differential diagnostic potential of otoacoustic emissions: a case study.

An 11-year-old boy was identified as having a profound sensorineural hearing loss accompanied by clear click-evoked otoacoustic emissions. Further diagnostic testing by means of electrocochleography and auditory brainstem responses indicated a predominantly retrocochlear disorder with good cochlear function. However, radiological investigation ruled out the presence of any material space-occupying lesion. This case illustrates the contribution that can be made by otoacoustic emission testing to differential diagnosis.

Child↗
PubMed1989

Relative benefits of stepped and constant bore earmoulds: a crossover trial.

Twenty-one first-time hearing aid candidates took part in a crossover trial which compared a stepped earmould of the 8CR design with a standard constant-bore earmould, each fitted to a low-powered National Health Service behind-the-ear hearing aid. Before fitting the aid, and also after 2-week trials with each earmould, aided speech-in-noise discrimination scores were obtained, along with subjective ratings according to a series of descriptive scales, and overall preference for one or other of the aids. Aided speech-in-noise scores were, on average, 2.4% higher for the stepped earmould. Two-thirds of the subjects preferred the stepped earmould and it was also rated as more clear on a clear-hazy descriptive scale. After the 4 week trial period, there was a tendency for the stepped earmould to be preferred by subjects with more sensitive hearing thresholds at 2 kHz and higher aided speech-in-noise scores with either earmould, although this was not true at the initial fitting.

Adult↗
PubMed1989

Comparison of manual and computer-controlled self-recorded audiometric methods for serial monitoring of hearing.

Manual and self-recorded audiograms obtained from 240 ears on two occasions 2-3 years apart were compared, with the objective of establishing the preferred method for serial monitoring of hearing thresholds. The self-recording method incorporates an objective scoring algorithm which is compared with subjective scoring carried out independently by two experienced audiology staff members. The objective scoring method agreed well with the subjective method but gives substantial advantages in terms of cost and freedom from scorer bias. The variability associated with manual audiometry was somewhat lower than that associated with self-recording audiometry when used for serial monitoring.

Algorithms↗
PubMed1987

Self-reported disability and handicap in the population in relation to pure-tone threshold, age, sex and type of hearing loss.

A self-administered questionnaire concerning auditory disability and handicap was completed by 1691 subjects who were part of a two-stage random sample of the UK adult population. A principal components analysis of questionnaire replies identified four components. They were interpreted as (a) disability for everyday speech, (b) disability for speech-in-quiet, (c) localisation, and (d) hearing handicap. Components (a) and (d) were the strongest, accounting for 68% of the variance. Subjects also performed pure-tone audiometry amongst other tests. Audiometric information was well described by a two-parameter model characterised by low-to-mid-frequency loss and high-frequency slope. All four components increased progressively with increasing low-to-mid-frequency loss, independent of high-frequency slope. They were best correlated with a binaural average over 0.5, 1 and 2 kHz weighted 4:1 in favour of the better ear, out of several audiometric descriptors examined. Sex and socio-economic group did not generally affect disability or handicap, but people of similar hearing impairment reported less disability and handicap as age increased. This is interpreted as over-compensation for the effects of age in self-report. There were three unexpected findings which may entail some changes in current thinking on the relationship between auditory impairment and self-perceived disability/handicap. Hearing losses incorporating a conductive component in the better ear were more disabling and handicapping than sensorineural losses of equal magnitude. Localisation ability and, to a lesser extent, general hearing handicap were more highly correlated with measures of impairment in the worse ear than in the better ear. There was little evidence for the concept of a 'low fence' in the relationship between impairment and either disability or handicap.

Adolescent↗
PubMed1986

Speech identification under simulated hearing-aid frequency response characteristics in relation to sensitivity, frequency resolution, and temporal resolution.

Word identification in noise was measured adaptively under flat and rising frequency response conditions to represent basic alternatives for a hearing-aid characteristic. The speech test results were compared with measures of sensitivity, loudness tolerance, frequency resolution, and temporal resolution in 23 hearing-aid users with mild or moderate sensorineural hearing losses. Subjects also rated the two frequency responses for preference and subjective quality. A paradoxical relationship was found whereby superior speech performance under the flat condition was associated with preference for the rising condition, and vice versa. No combinations of psychoacoustic variables satisfactorily explained either relative performance or preference, although high-frequency sensitivity and upward spread of masking were implicated. Absolute speech performance was related to sensitivity at 2 kHz, age, and sex, but not to frequency resolution once other factors were partialed. Temporal resolution was also a factor, but this was due largely to the influence of extreme values in two subjects. It is concluded that, for moderate degrees of hearing loss, speech identification in noise can be predicted from age, sex, and sensitivity with little advantage from recourse to measurement of frequency or temporal resolution.

Adult↗
PubMed1985

A simple clinical measure of frequency resolution.

A simple procedure for obtaining a 3-point approximation to a psychoacoustical tuning curve (PTC) using a clinical audiometer and tape recorder is described. Data from 45 normally-hearing subjects are presented in terms of distributions of scores amongst subjects and repeatability within subjects. The procedure has proven to be rapid and tractable and provides results which are comparable to more time-consuming methods.

Adolescent↗
PubMed1984

Phasor admittance measurements of the middle ear. I. Theoretical approach.

A parallel two-piston model of the middle ear is described. One piston represents vibrations of the ossicular chain and closely coupled vibrations of the tympanic membrane. The other piston represents uncoupled vibrations. To a first approximation, it is assumed that acoustic reflexes modify the former and tympanometry principally modifies the latter, although a comodulation model is also considered. The performance of the model is evaluated in terms of the trajectories of the input admittance phasor resulting from increases in stiffness assumed to occur during acoustic reflexes or tympanometry. This phasor trajectory approach places the various morphological categories of normal acoustic reflexes and tympanograms, including W-notched tympanograms, along a simple continuum. The model leads on to suggest a method by which the parameters of the two pistons can be evaluated using acoustic reflex and tympanogram data at two probe tone frequencies. The method is utilised in the subsequent paper.

Acoustic Impedance Tests↗
PubMed1984

Phasor admittance measurements of the middle ear. II. Normal phasor tympanograms and acoustic reflexes.

Phasor admittance trajectories obtained during tympanometry and acoustic reflex measurements at 220 and 660 Hz were obtained from 67 normal ears. The distributions of natural frequency and resistance derived from these phasor trajectories provide normative data for the technique. Median values of 817 and 714 Hz for natural frequency were obtained respectively for tympanometry and acoustic reflexes. Median resistances were 139 and 555 ohms. The distributions of these parameters from tympanometry and acoustic reflexes were significantly different for both resistance and natural frequency, supporting the assumption that the two procedures measure different aspects of middle-ear vibration, which we have attributed to ossicular chain vibration and to uncoupled vibration of the tympanic membrane. Correlation data are also consistent with this assumption.

Acoustic Impedance Tests↗