Maximum stable gain and fitting range of percutaneously applied bone conduction devices

to measure the maximum stable gain (MSG, the feedback limit) and its variability in users with two percutaneous power bone conduction devices (BCDs), to determine an MSG-based fitting range, and to measure the available aided dynamic range. The MSG was determined with the BCD attached to a participant’s head. The BCD output was measured on a skull simulator. A fitting range was derived using the speech intelligibility index. 42 adult BCD users. The average and range of the MSG was 13.3 ± 3.2 dB for device 1 and 16.1 ± 5.90 dB for device 2. The fitting range is 35–40 dB HL for a good understanding of soft speech and 45–50 dB HL for moderate-to-sufficient understanding of speech at a normal level in at least 50% of the cases with this hearing loss. The output for common speech levels is not limited by the maximum force output, except at low frequencies. For users of a percutaneous power BCD, the maximum applicable gain is limited by feedback and is smaller than the full-on gain. Consequently, BCDs enable sufficient speech intelligibility only for mild-to-moderate sensorineural hearing loss. The aided dynamic range is adequate for hearing thresholds within this fitting range.

本研究旨在测量两款经皮式动力型骨传导助听设备（bone conduction devices, BCDs）使用者的最大稳定增益（Maximum Stable Gain, MSG，即反馈极限）及其变异性，确定基于MSG的适配范围，并评估可用助听动态范围。MSG的测量需将骨传导助听设备佩戴于受试者头部，设备输出则通过颅骨模拟器完成测定。适配范围通过言语可懂度指数（Speech Intelligibility Index, SII）推导得出。本研究共纳入42名成年骨传导助听设备使用者。两款设备的MSG平均值及标准差分别为：设备1为13.3±3.2 dB，设备2为16.1±5.90 dB。针对此类感音神经性听力损失患者，适配范围设定为：若要清晰听清轻声言语，适配范围为35~40 dB 听力级（Hearing Level, HL）；若要在至少50%的日常场景中实现中等程度且足够的正常语速言语理解，则适配范围为45~50 dB HL。除低频段外，常规言语强度下的设备输出不受最大力输出限制。对于经皮式动力型骨传导助听设备使用者而言，最大可用增益受反馈效应制约，且低于满增益输出。因此，经皮式动力型骨传导助听设备仅对轻至中度感音神经性听力损失患者可实现足够的言语可懂度。助听动态范围可满足该适配范围内的听阈需求。