A novel method for objective in-situ measurement of audibility in bone conduction hearing devices – a pilot study using a skin drive BCD

Objective measurement of audibility (verification) using bone conduction devices (BCDs) has long remained an elusive problem for BCDs. For air conduction hearing aids there are well-defined and often used objective methods, and the aim of this study is to develop an objective method for BCDs. In a novel setup for audibility measurements of bone-anchored hearing aid (BAHA) attached via a soft band, we used a skin microphone (SM) on the forehead measuring in-situ sound field thresholds, maximum power output (MPO) and international speech test signal (ISTS) responses. Five normal-hearing persons. Using the electrical output of SM it was possible to objectively measure the audibility of a skin drive BCD, presented as an eSPL-o-gram showing thresholds, MPO and ISTS response. Normalised eSPL-o-gram was verified against corresponding FL-o-grams (corresponding force levels from skull simulator and artificial mastoid (AM)). The proposed method with the SM can be used for objective measurements of the audibility of any BCDs based on thresholds, MPO and speech response allowing for direct comparisons of hearing and BCD output on the same graph using an eSPL-o-gram. After normalisation to hearing thresholds, the audibility can be assessed without the need for complicated calibration procedures.

使用骨传导设备（bone conduction devices, BCDs）开展可听度客观测量（验证）长期以来都是骨传导设备领域一道悬而未决的难题。针对气导助听器，学界已形成成熟且广泛应用的客观测量方法，本研究旨在开发适配骨传导设备的客观测量方案。

本研究搭建了一套针对经软带佩戴的骨锚式助听器（bone-anchored hearing aid, BAHA）的可听度测量新型装置，通过前额处的皮肤传声器（skin microphone, SM）采集原位声场阈值、最大输出功率（maximum power output, MPO）与国际言语测试信号（international speech test signal, ISTS）的响应数据，共招募5名听力正常受试者参与实验。

借助皮肤传声器的电输出信号，可客观测量皮肤驱动型骨传导设备的可听度，所得结果以等效声压级图谱（eSPL-o-gram）呈现，涵盖阈值、最大输出功率与国际言语测试信号响应三项指标。研究将归一化后的等效声压级图谱与对应力级图谱（FL-o-grams，即源自颅骨模拟器与人工乳突（artificial mastoid, AM）的匹配力级数据）进行比对，验证了该方法的有效性。

本研究提出的基于皮肤传声器的测量方法，可基于阈值、最大输出功率与言语响应指标，对任意骨传导设备的可听度开展客观测量，支持在同一图谱中直接对比听力与骨传导设备的输出表现，仅需采用等效声压级图谱即可实现。将图谱归一化至听力阈值后，无需复杂的校准流程即可完成可听度评估。