Optical measurements of eardrum vibrations and sound propagation in the ear canal for the fitting of active middle ear implants

Abstract

Background

Middle ear implants (MEI) are for the medical rehabilitation of the hearing function in case of sound conduction hearing losses as well as cochlear hearing losses and their combinations.

Objectives

An objective tool to reach the best fitting of the external worn sound processors is essential for patients who do not want or cannot participate in the fitting process.

Methods

In addition to Laser-Doppler-Vibrometry (LDV) measurement, the sound pressure was measured distant to the eardrum to attain additional information for comparison. Three groups of patients with different middle ear characteristics were examined.

Results

Because of the large spreading of measuring results even within a patient group with similar eardrum and middle ear conditions it is difficult to develop characteristic diagrams which represent the mean values of eardrum displacements with different sound processor adjustments being the base for normative data courses.

Conclusions and Significance

The LDV measurements can be used as a tool for fitting sound processors by finding individual maximum eardrum velocities in the frequency range 125 Hz to 8 kHz. In comparison to acoustical measurements the optical measurements have advantages concerning lower variations of measurement values, higher spectral resolution, and robustness against disturbing acoustic noise, especially at low frequencies.

Chinese abstract

背景：对于声传导性听力损失以及耳蜗性听力损失及其组合, 中耳植入体（MEI）可用于听力功能的医学康复。

目的：对于不想或不能参与验配过程的患者来说, 要实现外部佩戴声音处理器的最佳拟合, 目的性工具是必不可少的。

方法：除了激光多普勒振动法 (LDV) 测量外, 还测量了远离鼓膜的声压, 以获得额外的信息用于比较。对三组不同中耳特征的患者进行了检查。

结果：即使在具有相似鼓膜和中耳条件的患者组内, 测量结果也会分布广泛。因此, 很难制作这样的特征图, 它代表具不同声音处理器调整的鼓膜位移平均值, 是规范数据课程的基础。

结论和意义：LDV 测量可用作拟合声音处理器的工具, 方法是找到 125 Hz 至 8 kHz 频率范围内的单个最大鼓膜速率。与声学测量相比, 光学测量具有测量值变化更小、光谱分辨率更高和对干扰噪声的抵御性等优势, 尤其是在低频时。

Keywords:

• Laser-Doppler-Vibrometry (LDV)
• middle ear implant
• floating mass transducer (FMT)
• ear canal acoustics
• sound processor

Acknowledgments

The technical support of the Polytec staff (Waldbronn, Germany) is gratefully acknowledged. The authors thank the fourteen patients who patiently participated in this study.

Disclosure statement

The authors declare that they have no conflict of interest.

Additional information

Funding

This work was supported by MED-EL GmbH, Innsbruck, Austria.