An Evaluation of Acoustic and Perceptual Effects of Feedback Management in Hearing Aids

Abstract

The present study aimed at evaluating the efficacy of the feedback reduction methods in the hearing aid, namely the phase cancellation algorithm and the use of acoustic modification (damper) in the ear mould using insertion gain measure and Speech Identification Scores (SIS). The data were collected from 60 ears of 30 children who had severe to profound hearing losses in both •ears. The results indicated that there was an increase in the gain available as well as the output with the activation of feedback management and with the use of dampers. The behavioural measure, the speech identification scores, was higher with the activation of feedback management method and dampers compared to without them. The increase in gain can be attributed to the principle of working of phase cancellation method which reduces the feedback so that useful gain can be increased. As the dampers smoothen the frequency response at mid frequencies, a greater available gain is possible at mid- and high- frequencies. The increase in the available gain along with the efficient cancellation of feedback may be attributed to improved speech identification scores in the condition with feedback management activated and with the use of dampers. The findings of the study support the necessity of use of feedback management method like phase cancellation algorithm in digital hearing aids and dampers in analog hearing aids in children with severe to profound hearing loss.