Comparison Between Outcomes Using Preferred Gain and Prescribed Gain Formulae in Experienced Adult Hearing Aid Users

Abstract

Prescriptive formulae prescribe gains based on different formulae that in turn are based on different rationales. But it has been noted by several authors that the gains prescribed by the prescriptive formulae may be different from the preferred gain settings. This study was done with the aim to compare the gain provided using the two most commonly used prescriptive formulae, NAL NL-1 and DSL[i/o] and compare this with the preferred gain settings. Ten subjects, in the age range of 30 to 75 years, who were regular users of hearing aids since more than twelve months were taken up for the study. The measures used for comparison were overall aided gain, gain at various input levels (45 dB, 65 dB & 89 dB), Real Ear Insertion Gain, and Speech Identification Scores for all the conditions. Results revealed that majority of the participants needed a gain of about 10 dB higher than NAL-NL1 and about 5 dB higher than DSL [i/o] and for Indian population, higher gain is required at mid to higher frequencies. Comparison of SIS revealed that the speech perception at the preferred condition was the best followed by NAL-NL1 and DSL [i/o]. From the results, it can be noted that there is a difference between the prescribed gain settings and preferred gain settings and this might have to be done on a larger population to arrive at a more concrete findings.