Guidelines for quantification of noise-induced hearing loss in a medicolegal context.

OBJECTIVES: Guidelines published in 2000 by the authors are widely used by medical and legal professionals in the UK for diagnosis of noise-induced hearing loss in a medicolegal context. However, they cannot be used for quantification of the noise-induced hearing loss, which is required in most cases. This requirement is addressed. DESIGN: A method is developed here to quantify noise-induced hearing loss, thereby overcoming this shortcoming. SETTING: Assessment of noise-induced hearing loss in medicolegal cases. PARTICIPANTS: A consecutive series of 124 cases of noise-induced hearing loss is used for evaluation. MAIN OUTCOME MEASURE: Magnitude of noise-induced hearing loss based on hearing threshold levels averaged over the frequencies 1, 2 and 3 kHz. RESULTS: The rationale of the method, practical application and three worked examples are developed. A simpler short-cut method is developed and shown to be equivalent to the full method in most cases. CONCLUSIONS: The method offers a practical approach to quantification of noise-induced hearing loss.

Asymmetric sensorineural hearing thresholds in the non-noise-exposed UK population: a retrospective analysis.

OBJECTIVES: To estimate the distribution of inter-aural sensorineural hearing threshold level differences in the non-noise-exposed adult population of the UK. SETTING: A two-stage population study carried out in 1979-1986, initially by postal questionnaire, followed up in a proportion of participants by clinical and audiological examination. PARTICIPANTS: Volunteers (n = 48 313) initially selected at random from the electoral registers of four cities, subsequently selected at random from questionnaire respondents stratified by answers to questions about hearing. MAIN OUTCOMES MEASURE: Inter-aural hearing threshold level differences measured audiometrically, as a function of age and gender. RESULTS: Tables of inter-aural threshold level differences provided as a resource with potential medicolegal, clinical and research applications. Based on the average of the frequencies 0.5, 1, 2 and 4 kHz, approximately 1% of the general UK population aged 18-80 years have an asymmetry of 15 dB or more. The prevalence is greater in older than in younger people. CONCLUSIONS: Inter-aural threshold differences greater than attributable to measurement error are not uncommon in the adult population, even after screening for conductive hearing loss and substantial noise exposure. They are typically of unknown origin.

Masking of the non-test ear in speech audiometry.

Masking of the non-test ear is often needed in speech audiometry but the methods for such masking have not been well defined. 'White' or 'speech' noise is commonly provided by audiometers for this purpose, and the many problems and uncertainties in their calibration and effectiveness are discussed; data on these aspects are presented with respect to some current audiometers and Fry's and AB(S) PB-word lists. Formulae are given for estimating the possible need for masking, calculating the required dial level of masking noise for a given dial level of speech signal, and assessing the extent to which cross-masking may be affecting the results. The formulae presented are applicable for earphone listening only.

Masking of the non-test ear in tone decay, Békésy audiometry, and SISI tests.

Masking of the non-test ear is frequently required in tone decay, Békésy audiometry and SISI tests; without it, serious misdiagnoses can result. Methods are given for calculating the dial levels of masking noises to be delivered and the extent of possible cross-masking. The methods are subdivided according to whether the tests to be employed are fixed-frequency or sweep-frequency, and to whether masking function data are available from previous use of shadow masking. In difficult cases, careful preliminary shadow-masking procedures and subsequent use of fixed-frequency tests is recommended.

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.

Measurement and management of tinnitus. Part I. Measurement.

This paper comprises mainly a description of the clinical practice and experience of the Tinnitus Clinic at the General Hospital, Nottingham, which has evolved as a result of and during the course of a 3-year DHSS-sponsored study of the efficacy of tinnitus maskers. The paper is supported by some experimental data from laboratory, epidemiological and clinical studies, and by information on the number of patients who can be seen, the staff required and the methods used in the clinic.