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.