Evaluation of a Remote Microphone System with Tri-Microphone Beamformer

Abstract

Background:

Children with hearing loss often experience difficulty understanding speech in noisy and reverberant classrooms. Traditional remote microphone use, in which the teacher wears a remote microphone that captures her speech and wirelessly delivers it to radio receivers coupled to a child’s hearing aids, is often ineffective for small-group listening and learning activities. A potential solution is to place a remote microphone in the middle of the desk used for small-group learning situations to capture the speech of the peers around the desk and wirelessly deliver the speech to the child’s hearing aids.

Purpose:

The objective of this study was to compare speech recognition of children using hearing aids across three conditions: (1) hearing aid in an omnidirectional microphone mode (HA-O), (2) hearing aid with automatic activation of a directional microphone (HA-ADM) (i.e., the hearing aid automatically switches in noisy environments from omnidirectional mode to a directional mode with a cardioid polar plot pattern), and (3) HA-ADM with simultaneous use of a remote microphone (RM) in a “Small Group” mode (HA-ADM-RM). The Small Group mode is designed to pick up multiple near-field talkers. An additional objective of this study was to compare the subjective listening preferences of children between the HA-ADM and HA-ADM-RM conditions.

Research Design:

A single-group, repeated measures design was used to evaluate performance differences obtained in the three technology conditions. Sentence recognition in noise was assessed in a classroom setting with each technology, while sentences were presented at a fixed level from three different loudspeakers surrounding a desk (0, 90, and 270° azimuth) at which the participant was seated. This arrangement was intended to simulate a small-group classroom learning activity.

Study Sample:

Fifteen children with moderate to moderately severe hearing loss.

Data Collection and Analysis:

Speech recognition was evaluated in the three hearing technology conditions, and subjective auditory preference was evaluated in the HA-ADM and HA-ADM-RM conditions.

Results:

The use of the remote microphone system in the Small Group mode resulted in a statistically significant improvement in sentence recognition in noise of 24 and 21 percentage points compared with the HA-O and HA-ADM conditions, respectively (individual benefit ranged from −8.6 to 61.1 and 3.4 to 44 percentage points, respectively). There was not a significant difference in sentence recognition in noise between the HA-O and HA-ADM conditions when the remote microphone system was not in use. Eleven of the 14 participants who completed the subjective rating scale reported at least a slight preference for the use of the remote microphone system in the Small Group mode.

Conclusions:

Objective and subjective measures of sentence recognition indicated that use of remote microphone technology with the Small Group mode may improve hearing performance in small-group learning activities. Sentence recognition in noise improved by 24 percentage points compared to the HA-O condition, and children expressed a preference for the use of the remote microphone Small Group technology regarding listening comfort, sound quality, speech intelligibility, background noise reduction, and overall listening experience.

Key Words

adaptive directional microphone - pediatric audiology - remote microphone system - small group - speech perception

This research was partially funded by a grant from Phonak, LLC. These data have not been presented in any other journal or at any professional meeting.

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