Evaluation of a Remote Microphone System with Tri-Microphone Beamformer

Abstract

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.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.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.Fifteen children with moderate to moderately severe hearing loss.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.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.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.

Remote Microphone Systems for Cochlear Implant Recipients in Small Group Settings

“…Similar improvements with adaptive multiple-microphone beamforming technology were reported for hearing aid users relative to a hearing-aid alone. 13 Across SNRs, the use of the remote microphone with multitalker network improved speech recognition in noise by an impressive average of 28 to 49 percentage points relative to the CI alone. The greater improvement in speech recognition in noise obtained with the multi-talker network relative to the adaptive multiple-microphone beamformer is likely due to differences in microphone positioning and technology features.…”

“…Specifically, a remote microphone with an adaptive multiple-microphone beamformer may be placed in the center of the small group, and the beam (i.e., polar lobe) may be automatically steered toward the direction with the best SNR to allow wireless delivery to the CI processor. Wolfe and colleagues 13 report that remote microphone systems with adaptive multiple-microphone beamforming significantly improved speech recognition in small group settings by 24 percentage points in a group of 15 children using hearing aids relative to their aids alone. However, to date, no studies have explored the potential benefits of adaptive multiple-microphone beamforming for CI recipients.…”

Why do many children who are hard of hearing not use remote microphones to compensate for their hearing loss?

“…Prior research has shown that, on average, the use of RM improves children's speech perception in complex listening environments, and the insufficient benefit for some children has not been explored in-depth in many studies. Wolfe, Duke [ 1 ] explored modern RM with adaptive functions for solving the ineffectiveness of earlier technologies for small-group listening and interactive lessons [ 1 ]. Modern types of devices, through different functions and modes, focus on the special needs of children in different listening situations.…”

“…Despite the use of primary compensatory devices (hearing aids/cochlear implants), children who are hard of hearing (HoH) are disadvantaged compared to their peers. These disadvantages include speech recognition under noisy conditions or understanding speech at a greater distance [ 1 , 2 , 3 ]. This do not necessarily mean that the child cannot hear or understand, but they usually find listening more difficult and have to exert more effort than their classmates with normal hearing [ 4 ].…”

Remote-Microphone Benefit in Noise and Reverberation for Children Who are Hard of Hearing

“…[24][25][26][27][28] HAs alone may not be able to overcome the adverse effects of noise, distance, and reverberation in classrooms since amplification is applied to whatever combination of signals reach the microphone. [29][30][31] However, children who are hard of hearing and who have greater aided audibility have been shown to demonstrate better speech understanding in a variety of acoustic environments than children with poorer audibility. 4,[32][33][34][35] It is possible that better-aided audibility with HAs could correspond to better speech understanding when those HAs are used with RM systems than when HAs with poorer aided audibility are used with RM systems.…”