骨导耳间衰减与MOC反馈对听觉掩蔽效应的影响

Bone conduction hearing-aids are widely used, requiring higher-accuracy test of bone conduction hearing thresholds. The Hood plateau method, widely used in bone conduction hearing thresholds test, may sometimes fail to finding the effective auditory masking plateau, and lead to inaccurate or even wrong results. Our previous findings show that there is frequency related interaural attenuation, and the asymmetry in translational and compressional bone conduction between ipsilateral and contralateral ear. Furthermore, compressional bone conduction makes more contribution to hearing threshold than the translational one, which suggests that there exist differences of bone conduction masking effect at different frequencies. As reported in literature, MOC feedback can cause central masking which leads to elevation of hearing thresholds. We suppose above factors are related to the inaccurate testing results of bone conduction thresholds. Therefore, this study aims at investigating the interaction mechanism of the frequency related bone conduction interaural attenuation and central masking to the masking effects during bone conduction test. On the basis of previous studies, LDV，DPOAE and cochlear microphonic potential(CM) measurements will be used to record the basilar membrane response of the cadaver and animal model under different masking conditions,(1)to analyze the different interaction results between translational and compressional bone-conduction with masking noise by recording the BM response at its characteristic frequency location; (2) to analyze the influence of MOC feedback on masking effect. These result could help to clarify the factors which affect the accuracy of bone conduction threshold test, and provide experimental basis for improving performance of bone conduction hearing-aids.

骨导助听的广泛使用对骨导听阈的准确评估提出了更高的要求。目前采用的Hood平台法测试骨导听阈，有时存在找不到掩蔽平台导致测听结果不准或错误。前期研究结果表明存在骨导耳间衰减的频率相关性与移动、压缩式骨导的非对称性，且压缩式比移动式骨导对听阈影响更大，提示骨导掩蔽效应在不同频率存在差异；文献报道MOC反馈作用可引起中枢掩蔽，进而导致双耳听阈升高。以上因素可能与骨导测听不准存在相关性。因此，本项目针对骨导耳间衰减的频率相关性与MOC反馈对骨导测试听觉掩蔽效应的作用机制进行研究。拟在前期研究基础上，采用 LDV、耳声发射和耳蜗微音电位测量技术，对颅骨及动物模型在不同掩蔽状态下的基底膜响应进行测试记录，分析移动及压缩式骨导与掩蔽声在基底膜特征频率处响应的相互作用;分析MOC反馈对掩蔽效应及骨导听阈的影响。以期明确影响骨导听阈测试准确性的因素，为完善Hood平台法及改善骨导助听效果提供实验依据。

经颅传递是骨导听觉相对气导听觉最为显著的特征，但是其耳间衰减的机制及其对骨导听觉的影响尚未阐明。经颅衰减所导致的交叉听觉可能引起骨导听阈测量准确性问题，同时还会对声源定位产生影响。因此，本课题系统性地研究骨导外周听觉系统生物力学机制，并针对骨导耳间衰减进行了深入研究。.我们的研究分为以下几个部分。（1）应用激光多普勒振动测量技术，研究了骨导激励下颅骨、耳蜗的振动模式；（2）应用有限元技术，仿真了骨导激励下颅骨的振动及耳蜗行波的产生；（3）在以上研究基础上，定量研究了经颅衰减的频率相关性，阐明其和颅骨振动模式的关系；并对骨导下声源定位机制进行了探索性研究。(4) 针对MOC控制与听觉掩蔽效应进行了动物模型研究。.本研究 (1) 结合医学与工程的研究手段，对骨导听觉机制进行了系统研究；(2) 对于骨导下声源定位影响因素及机制的研究具有特色，提出了交叉听觉的干扰作用。本研究的成果为深入理解骨导机制提供了基础数据，为进一步开发骨导相关产品提供参考。