Impact of binaurally balanced versus binaurally imbalanced hearing aids on speech perception in noise

Abstract

Introduction: Management of hearing loss primarily involves hearing aids. These have been shown to improve quality of life. However, despite significant advancements in hearing aid technology over the past 50 years, poor speech perception in noise has remained a common complaint. Speech understanding in noise is shown to be better with a bilateral versus a unilateral fitting when the hearing loss is bilateral. However, it is not known whether binaural balance between the hearing aids is also essential, and if imbalance could adversely affect speech perception in noise. This study aimed to investigate: 1. if an imbalance between bilaterally fitted hearing aids has an effect on speech perception in noise. 2. If variables such as self-perceived hearing handicap, audiometric thresholds, and speech recognition ability can help explain any relationship between binaural imbalance and speech perception in noise. Methods: Twenty-one participants with atleast mild-moderate hearing loss bilaterally and good speech recognition ability participated. Participation involved a 2 hour testing session that included a hearing test, a hearing aid fitting, and the Hearing in Noise Test (HINT) in 3 balance conditions. The hearing aids were considered to be binaurally balanced once both had been fitted to NAL-NL2 targets. The gain across all frequencies and levels was decreased in one hearing aid by 5dB and then by a further 5dB. The HINT was carried out in each of these 3 balance conditions (balanced, 5dB imbalanced, and 10dB imbalanced). The hearing aids used in this study contained binaural beamforming technology. Results: A one-way ANOVA revealed that the poorer speech perception in noise found in the 5dB and 10dB imbalanced conditions when compared to the balanced condition were not statistically significant. Speech perception in noise was statistically significantly worse in the 10dB compared to the 5dB imbalanced condition. Pearson correlations showed higher audiometric thresholds, lower PI-MAX, and worse Hearing Handicap Inventory scores to be associated with worse speech perception in noise in the 10dB imbalanced condition. Conclusions: Speech perception in noise is likely to be significantly worse when there is a 10dB imbalance between the hearing aids. These results have a number of implications for clinical practice, including the importance of accurately carrying out verification of hearing aids. These findings have contributed towards better understanding of the factors that can lead to poor speech perception in noise, and may thus contribute towards reducing this problem. More research is required to confirm these findings and to further explore this area.