Measuring auditory filters efficiently

Abstract

Knowledge of the frequency‐resolving power of an individual's ear may be helpful in hearing aid selection and in adjustment of multichannel hearing aids. A method using threshold measurements with notched noises, developed by Patterson, has been adopted as the best method. Patterson proved that the filter form can be assumed to be composed of two rounded exponential functions: W(g) = (1 − r) (1 + pg) × exp(− pg) + r, where g is the relative deviation from the filter center frequency for off‐frequency listening, p defines the steepness of one of the filter skirts, and r limits the dynamic range of the filter. Up until now, auditory filters have been measured very precisely in conjunction with research requiring many threshold measurements. In clinical work, time is an important factor. For this reason we investigated the effect of a reduction of the number of threshold measurements on fitted filter characteristics. Filter estimates of 33 subjects (normal hearing, sensorineurally hearing impaired, and conductively hearing impaired) for three different measurement conditions have been analyzed. First, thresholds measured with five symmetrical and eight asymmetrical noises determined the parameters of the filter precisely. Second, the parameters were calculated with a reduced number of thresholds. Third, an alternative fitting procedure was employed. The influence of the reduction of the thresholds on the filter parameters, the effects of the alternative fitting procedure, and the need for retest measurements will be discussed.