Benefits of Binaural Amplification in Participants with Asymmetric Hearing Impairment

Abstract

Binaural hearing involves the integration of signals from each of the two ears into a single hearing sensation. The advantages of loudness summation, localization and discrimination enhancement especially in noise are a result of this binaural hearing process. However, when the signals to each ear are disproportionate with each other in an individual with hearing impairment, binaural integration process is less effective and binaural advantages are correspondingly diminished or even lost (Davis & Haggard, 1982). The present study was undertaken to assess the benefits of binaural amplification over monaural amplification in individuals with sensorineural hearing loss with various degrees of asymmetry. Twenty-two individuals with post-lingually acquired bilateral sensorineural hearing loss served as participants in this study. The participants were assigned to one of the three groups based on the degree of hearing loss in the ears. The most comfortable levels (MCL), speech recognition scores (SRS) and speech recognition threshold in noise (SRT) were established for each participant in the three-aided conditions- amplification to the better ear, to the poorer ear and to both ears. It was observed that lowest MCL was obtained in the binaural amplification condition compared to the monaural amplification condition in all three groups of participants. For speech recognition in quiet, it was found that providing binaural amplification did not result in significant improvement over monaural amplification for participants with bilateral symmetric hearing loss. In participants with asymmetric hearing loss (Groups II & III), providing binaural amplification resulted in improved speech recognition performance compared to monaural amplification either to better or poorer ear. It was observed that the participants obtained higher speech recognition threshold in noise (SNR) with binaural amplification than with monaural amplification condition.