An evaluation of high-frequency audiometry suitable for routine clinical use

A pilot investigation of high-frequency audiometry in obscure auditory dysfunction (OAD) patients

The diagnosis of obscure auditory dysfunction (OAD) has been an elusive one, based primarily upon reports of poor speech perception in noise by the patient. Basic audiometric testing reveals hearing within normal threshold limits and it is thought that there may, in part be some subtle psychoacoustic and/or central auditory deficits causing this phenomenon. The use of high-frequency audiometry (HFA) as a test of subclinical cochlear damage has been well documented, especially to monitor the early effects of noise exposure and ototoxic drugs. However, it has not been used in the diagnosis of OAD patients. This study examines the use of HFA as an aid to the understanding of OAD pathophysiology. HFA was conducted on nine OAD subjects, each matched to two controls. Results indicate an elevated threshold amongst all frequencies (10-20 kHz) in OAD patients with significant differences occurring at 10, 14, 16 and 20 kHz. It could be postulated that OAD in fact, is the product of an ultra-high-frequency hearing impairment and its psychoacoustic sequelae. Furthermore, HFA may be a useful inclusion in a diagnostic test battery for OAD status. However, the degree to which it can be used may be limited due to the large intersubject variability in HFA thresholds in the normal population. It is suggested that further investigations into the ultra-high-frequency hearing abilities of OAD patients should be completed in the future.

An investigation of normally hearing subjects with tinnitus

The hearing sensitivity and psychological profile of 18 young subjects with tinnitus and normal hearing were investigated by pure-tone and high-frequency audiometry, notched-noise tests, auditory-brainstem responses, evoked otoacoustic emissions and Crown-Crisp experiential index. Psychoacoustical and brainstem tests were comparable to those of 19 normally hearing subjects without tinnitus. Otoacoustic emissions were worse in ears of tinnitus subjects. Neurotic personality traits were stronger in the tinnitus subjects. These traits may be secondary to otological dysfunction, or may contribute to complaint behaviour.

High-frequency monitoring using an electrostimulation audiometer

Electrostimulation audiometry can provide high-frequency bone-conduction threshold measurements. To evaluate the use of such an audiometer in monitoring hearing, the following areas were investigated. (1) The variability and repeatability of threshold measurements. (2) To see if the instrument could be used on the ward where the patient would have to wear ear plugs to attenuate background noise, the effect of occluding the ears was assessed. (3) The applicability of the instrument to the range of patients in whom monitoring would be appropriate, specifically the relationship between the patient's age and the effective upper frequency limit of the audiometer. The data showed a variability in threshold measurement that is quite comparable with that obtained with conventional audiometry but which became smaller at frequencies of 12 kHz and higher. There was no overall effect on the threshold of occluding the ears, which meant that the instrument can be used to monitor a non-isolated environment such as a ward. The effective cut-off frequency was about 9 kHz for patients aged 55 years, and so the use of an electrostimulation audiometer to monitor high-frequency auditory thresholds is restricted to younger patients.

High-frequency audiometry using precision earphones: reliability under laboratory and field conditions

New circumaural earphones were tested in the frequency range from 100 Hz to 20 kHz and compared to commonly used supra-aural earphones. The circumaural earphone HD 230 (Sennheiser) generates test stimuli at up to 20 kHz with almost constant sound pressure levels when its pos ed on an artificial ear. The reproducibility of hearing threshold mea ed with a new microprocessor-controlled Békésy audiometer using the ne was nearly as good as under free-field conditions. The practicabil diagnostic value of high-frequency audiometry have been demonstrated er field conditions. For this application, the good sound attenuation these earphones (30 dB above 1 kHz) are important. High-frequency he ds of healthy pupils and of pupils with a history of otitis media are kHz, the hearing threshold level difference between both groups reached 20 dB.

The role of high-frequency audiometry in early detection of ototoxicity

Ototoxicity is one of the unwanted side-effects of a number of medical drugs. As ototoxicity appears to be most pronounced in the higher frequencies, it can be assessed at an earlier stage by using high-frequency audiometry from 8 to 20 kHz. We have investigated the precision of these measurements. In spite of inaccuracies of headphone positioning, which may influence especially the high-frequency thresholds, standard deviations for frequencies above 8 kHz were obtained that were nearly as small as for audiometry up to 8 kHz. Age-related reference curves for the higher frequencies are presented. The results on 100 ears of patients treated with platinum-derivatives show the importance of high-frequency audiometry for the early detection of ototoxicity.