A review of hearing aid fitting procedures

Abstract

　There are two methods for adjusting the characteristics of hearing aids for individuals with impaired hearing: a comparative procedure and a prescriptive procedure. In practice, these two procedures are usually combined at hearing aid clinics. At present, the NAL-NL (National Acoustic Laboratory-nonlinear) and the DSL (Desired Sensation Level) procedures are generally used worldwide. Although no significant differences in speech perception have been seen between the NAL-NL and the DSL in several investigations, the DSL results in a loud sensation more often than the NAL-NL. The prescriptive target indicated by these procedures should be accomplished at the end stage of fitting, rather than at the start. For new hearing aid users, a procedure that starts with less acoustic gain and gradually reaches the final prescriptive target gain has been proposed. Investigating whether these prescriptive processes developed in English-speaking countries are valid for use in Japan will be important.