RP206 - Evaluation of a Dual Adaptive Remote Microphone System

Abstract:
Standard adaptive remote microphone (RM) systems increase progressively the RM gain when the ambient noise level exceeds an activation threshold in dB SPL. Dual adaptive RM systems increase progressively the RM gain in moderate noise but reach a plateau in RM gain after a 10-dB increase. Further increases in ambient noise result in a reduction in hearing aid gain with the goal of improving the SNR for the RM signal while optimizing listening comfort. The objective of this study was to compare speech recognition and subjective preferences of children using hearing aids with standard adaptive and dual adaptive RM systems.

Summary:
Objectives
Children with hearing loss experience difficulty with speech recognition in noisy (at signal-to-noise ratios [SNRs] commonly encountered in classroom settings) and reverberant situations and when the speech signal of interest originates from a distance. Remote microphone (RM) systems are the most effective technology to improve speech perception in noise for children who use hearing aids, cochlear implant, bone conduction devices, or ear-level radio receivers. Standard adaptive RM systems increase progressively the RM gain when the ambient noise level exceeds an activation threshold in dB SPL. A dual adaptive RM system increases progressively the RM gain in moderate noise but reaches a plateau in RM gain after a 10-dB increase. Further increases in ambient noise result in a reduction in hearing aid gain with the goal of improving the SNR for the RM signal while also optimizing listening comfort. The objective of this study was to compare speech recognition and subjective preferences of school-age children using hearing aids with standard adaptive and dual adaptive RM systems in a classroom environment.

Rationale
Research has clearly shown that RM systems provide significant improvement in speech recognition in noise for children with hearing loss. Research has also shown that use of adaptive RM systems results in better speech recognition in noise than what is obtained with use of fixed-gain RM systems. To date, there have been no published studies that examine potential differences between standard adaptive and dual adaptive RM systems.

Design
Twenty-five children with bilateral, mild to moderately severe hearing loss participated in the repeated measures design to evaluate device differences. Sentence recognition in quiet and in noise and subjective preferences were assessed in a classroom setting with each technology in several conditions to simulate common classroom listening situations. Performance was also assessed in the hearing aid only condition (i.e., no RM).

Results
Statistically significantly improvement in speech recognition was found with both RM systems compared to the no-RM condition. No significant differences in speech recognition in quiet or in noise were observed between the two adaptive RM systems in any test conditions. Additionally, participants did not report a significant preference for either RM system, although there was a non-significant trend toward an overall preference for the dual adaptive system in traditional classroom settings.

Conclusions
Use of standard and dual adaptive RM systems results in better speech recognition in quiet and in noise compared to use of hearing aids alone. There are no significant differences in speech recognition in noise between the standard adaptive and dual adaptive RM systems. Some children may prefer use of dual adaptive RM systems, presumably due to an improvement on listening comfort in high-level noise environments. Dual adaptive RM systems should be considered for children who complain of the RM signal being too loud in noisy environments.