LOUDNESS SCALING - A QUANTITATIVE INDICAT OR OF RECRUITMENT

Direkt loudness scaling has been known as an audiological tool for abo ut four decades. Although numerous publications have shown its clinica l importance, loudness scaling has not been used in audiology and hear ing aid fitting until now. This might be due to the lack of audiometer s equipped with loudness scaling devices as well as missing evidence f or its clinical applicability. In this study normal data for a single- step direct scaling procedure were established and loudness determinat ions of 105 patients with sensorineural hearing losses collected. The results show that normal level loudness functions exhibit very similar shapes for narrow band stimulation in the frequency range of 500 to 4 000 Hz. However, loudness scaling is affected by the gender of the sub jects: females scale systematically louder than do males. In hearing-i mpaired subjects the slopes of the level loudness functions tend to de crease with increasing hearing loss, indicating negative recruitment. This holds particularly true in the high-frequency range, e.g. at 4000 Hz. Our long-term experience with single-step direct loudness scaling has proven its clinical feasibility in typical patients of an audiolo gy unit. Loudness scaling will prove useful for the localization of he aring impairments, as it can be employed as a quantitative indicator o f recruitment without any restrictive preconditions. In addition, it a llows the evaluation of hearing aids and cochlear implants by frequenc y-specific gain measurement.