M. E. Lutman

The Distribution of Hearing Threshold Levels in the General Population Aged 18–30 Years

Hearing threshold levels at audiometric frequencies between 0.25 and 8 kHz were obtained by manual audiometry using 5-dB steps in adults aged 18-30 years, as part of a large random survey of hearing in the UK. After screening to ensure otological normality, including careful analysis of any noise exposure history, the median thresholds of the 241 screened subjects deviated from audiometric zero by an average of 4.3 dB over the frequencies from 0.5 to 4 kHz in the direction of poorer hearing. Even greater deviations were evident at 0.25, 6 and 8 kHz, consistent with the discrepancies between normal hearing threshold and ISO 389 standard reference zero that have been reported previously. Within the age band from 18 to 30 years, age did not influence hearing threshold levels. Socio-economic status defined by occupational group (manual or non-manual) had a significant effect at frequencies up to 2 kHz, with those in non-manual occupations having better hearing than those in manual occupations by an average of 2.4 dB, despite screening for middle-ear disease, noise exposure and other possibly confounding factors. In a screened sample, males had better hearing threshold levels than females, but this difference was sensitive to screening criteria. The unscreened sample had median hearing threshold levels that were at most 2 dB worse than the screened sample across the frequency range.

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.

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.

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.

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.

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.

Reliable identification of click-evoked otoacoustic emissions using signal-processing techniques

As neonatal hearing screening programmes based on click-evolved otoacoustic emissions (CEOAEs) become more common, there is a need for automatic scoring methods to classify responses systematically. Such methods must guard rigorously against errors that would pass a baby who would otherwise fail and be referred for further diagnostic testing. Preliminary analysis of a wide range of CEOAE waveform characteristics from adult and neonatal ears suggested that the most reliable measure on which to base an automatic method was the cross-correlation coefficient between replicate non-linear components. Further analysis of recordings from 2049 ears of 1102 neonates in neonatal intensive care units indicated that a cross-correlation coefficient greater than 0.5 was an appropriate criterion to distinguish a pass from a fail, with the following two provisos. The waveforms should be high-pass filtered to remove random low-frequency components before calculating the cross-correlation coefficient. The cross-correlation coefficient should relate to the time period from 6-16 ms after click onset. Using this method, 90% of recordings were automatically classified in agreement with a proven method of visual scoring. Only one ear without evidence of otoacoustic emission was passed by the automatic scoring method.

Relative benefits of linear analogue and advanced digital hearing aids

Speech recognition performance and self-reported benefitfrom linear analogue and advanced (digital) hearing aidswere compared in 100 first-time hearing aid users withmild-to-moderate sensorineural hearing loss fitted monaurally with a behind-the-ear (BTE) hearing aid in a single-blind randomized crossover trial. Subjects usedeach aid for 5 weeks in turn, with aid order balancedacross subjects. Three alternative models of digital hearing aid were assigned to subjects according to a balanceddesign. Aid type was disguised to keep subjects blind within practical limitations. Aided speech recognition performance in noise was measured at speech levels of 65 and 75 dB at a speech-to-noise ratio (SNR) of _2 dB forclosed sets of single words. Self-rated benefit was measured using the Abbreviated Profile of Hearing Aid Benefit (APHAB) and the Glasgow Hearing Aid Benefit Profile (GHABP). Quality of life, hearing aid use and user preferences were also assessed. Speech recognition scores with the digital aids were significantly better at 75 dB than with the analogue aids. Self-reported benefit (APHAB, GHABP) and improvement in quality of life were generally not significantly different between analogue and digital aids, although aversiveness measured with the APHAB was significantly lower with digital aids,and satisfaction measured with the GHABP was greater. The digital aids were preferred significantly more often than the analogue aids, with 61 subjects choosing their digital aid, 26 choosing the analogue aid, and nine being equivocal. Overall, this study shows advantages for advanced digital over simple linear analogue aids interms of both objective and subjective outcomes, although average differences are not large. Sumario Se comparó el desempeño para el reconocimiento del lenguaje y los beneficios relatados por 100 nuevos usuarios de auxiliares auditivos analógicos y digitales, con hipoacusia leve a moderada con curvetas monoaurales,en un estudio cruzado, aleatorio simple ciego. Los sujetos utilizaron cada auxiliar auditivo durante 5 semanas, con orden balanceado entre ellos. Se asignaron tres modelos alternativos de auxiliares digitales a los sujetos, conapego al diseño previsto. Se encubrió el tipo de auxiliar auditivo para evitar que los usuarios lo reconocieran. Se midió el reconocimiento del lenguaje en ruido, con amplificación, a niveles de lenguaje de 65 y 75 dB con una relación señal/ruido (SNR) de +2 dB, usando palabras sencillas en contexto cerrado. El beneficio autoevaluado se midió utilizando el Perfil Abreviado del Beneficio de Auxiliares Auditivos (APHAB) y el Perfil de Beneficio de Auxiliares Auditivos de Glasgow (GHABP). También seevaluaron la calidad de vida, el uso del auxiliar auditivo y las preferencias del usuario. La puntuación del reconocimiento del lenguaje a 75 dB, fue significativamentemejor con el auxiliar auditivo digital que con elanalógico. No hubo diferencia significativa entre ambos auxiliares auditivos, en el beneficio relatado (APHAB,GABP) o en la calidad de vida, aunque la aversiónmedida con el APHAB fue significativamente menor con los auxiliares digitales al igual que la satisfacción medidacon el GHABP. Hubo una preferencia significativa porlos auxiliares digitales; 61 sujetos eligieron los digitales,26 los analógicos y nueve no mostraron preferencia. Engeneral este estudio demuestra ventajas de los auxiliares auditivos digitales avanzados sobre los analógicos lineales, tanto en resultados subjetivos como objetivos, aunque las diferencias promedio no son muy grandes.

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.

The Feasibility of Using Oto-Acoustic Emissions to Monitor Cochlear Function During Acoustic Neuroma Surgery

The feasibility of using evoked oto-acoustic emission (EOAE) measurement for intra-operative monitoring of cochlear function was assessed during removal of an acoustic neuroma in a 53-year-old woman with normal hearing on the operated side prior to surgery. The high level of noise in the operating theatre was the only material problem encountered and this was not sufficient to prevent recording of identifiable waveforms. During manipulation of the brainstem, damage to the cochlea was indicated by an increase in EOAE latency and its eventual disappearance. A total hearing loss in the operated ear was revealed after surgery. Monitoring cochlear function with EOAEs is probably best considered at present as an adjunct to auditory brainstem response monitoring of the composite cochlea and eighth nerve, thus providing differential information.