(PP302) Electro-Mechanical Analysis of Remote Microphone Transparency for Bone-Conduction Systems

Rationale/

Purpose: Remote microphone systems are available for all categories of ear-level hearing assistive technology: hearing aids, cochlear implants, and bone conduction systems. As benefits have been documented for situations beyond the traditional classroom setting, and as options are available at lower costs or even as free accessory options in some instances, it is no surprise that patient use has increased. This clinic has experienced an increase in the number of systems utilized for children younger than 3 years old, predominantly due to the benefits of remote microphone technology that have been demonstrated for home use and availability of low-cost or free remote microphones. Although guidelines exist for assessing remote microphones (American Academy of Audiology, 2008; 2011), options are limited when considering young or difficult-to-test children who utilize bone conduction devices. The purpose of this study is to describe the use of a skull coupler to perform an electro-mechanical verification of transparency of remote microphones that stream to bone conduction systems.

Methods: The transparency test follows the electroacoustic verification procedure outlined in the Clinical Practice Guidelines for Remote Microphones (AAA 2008, 2011). As in the guidelines for hearing aids, a broad spectrum speech stimulus presented at 65 dB SPL will be used as the input to the bone conduction microphone or remote microphone. The primary modification for a bone conduction system is use of a skull coupler and a force level (FL) decibel reference. Remote microphone transparency will be evaluated by comparing the output force level of the bone conduction system alone to the output force level when the remote microphone is connected and streaming. Although emphasis is placed on 750, 1000 and 2000 Hz (AAA 2008, 2011), comparisons will be made across 250-12,500 Hz.

Three remote microphones that are in common use will be assessed for transparency. One microphone is designed specifically for the classroom and two are available as accessories. When available, remote microphone parameters will be adjusted systematically to quantify the effects on transparency.

Results: Transparency is not always attainable. Some remote microphones have more controls available to the clinician for modifying output than others. Data collection is ongoing; findings will be presented at AAA.

Conclusions:  Electro-mechanical verification is one aspect to consider when managing a remote microphone for an individual who uses a bone conduction system. Skull couplers are available to clinics, making the procedures described here accessible for implementation. Ideally, information about transparency should be taken together with functional measures, and additional work is needed in this area to further understand how settings should be adjusted to maximize benefit for the individual.