Prescription of Hearing Aids using Auditory Steady State Responses (ASSR)

Abstract

Hearing aid prescription involves setting the gain at different frequencies and other parameters including compression ratio and compression knee-point. Verification of hearing aid can be done using subjective techniques such as functional gain and objective techniques such insertion gain or electrophysiological tests. In the present study, intensity-amplitude functions were obtained from measures of loudness growth using Auditory Steady State Responses (ASSR). Using this, the gain and compression ratio of the hearing aid were estimated. The relationship between amplitude and intensity of the ASSR was compared in a group of adults having normal hearing with that adults having moderate and moderately-severe sensorineural hearing loss. This was done to propose a method to derive information on hearing aid characteristics from the amplitude- intensity function of the ASSR. This procedure enabled determination of some basic properties of hearing aids, such as average gain, compression ratio. The study also aimed at comparing the gain and compression ratio estimated by ASSR with that predicted by NAL-NL1 and FIG6 prescriptive procedures. From the results of the study it can be inferred that, the gain prescribed by ASSR-PF can also be useful in prescribing hearing aid gain as it was comparable with other prescriptive formulae. Thus, the ASSR serves as an objective tool in verifying the hearing aid prescription process for difficult-to-test population such as infants, young children in whom reliable behavioural responses cannot be obtained