Lewis James D, Neely Stephen T
Boys Town National Research Hospital, 555 North 30th Street, Omaha, Nebraska 68131, USA.
J Acoust Soc Am. 2015 Aug;138(2):977-93. doi: 10.1121/1.4927408.
A method to transform the impedance measured in the ear canal, ZEC, to the plane of the eardrum, ZED, is described. The portion of the canal between the probe and eardrum was modeled as a concatenated series of conical segments, allowing for spatial variations in its cross-sectional area. A model of the middle ear (ME) and cochlea terminated the ear-canal model, which permitted estimation of ME efficiency. Acoustic measurements of ZEC were made at two probe locations in 15 normal-hearing subjects. ZEC was sensitive to measurement location, especially near frequencies of canal resonances and anti-resonances. Transforming ZEC to ZED reduced the influence of the canal, decreasing insertion-depth sensitivity of ZED between 1 and 12 kHz compared to ZEC. Absorbance, A, was less sensitive to probe placement than ZEC, but more sensitive than ZED above 5 kHz. ZED and A were similarly insensitive to probe placement between 1 and 5 kHz. The probe-placement sensitivity of ZED below 1 kHz was not reduced from that of either A or ZEC. ME efficiency had a bandpass shape with greatest efficiency between 1 and 4 kHz. Estimates of ZED and ME efficiency could extend the diagnostic capability of wideband-acoustic immittance measurements.
本文描述了一种将耳道内测得的阻抗ZEC转换为鼓膜平面处阻抗ZED的方法。探头与鼓膜之间的耳道部分被建模为一系列串联的锥形段，以考虑其横截面积的空间变化。中耳（ME）和耳蜗的模型作为耳道模型的终端，从而可以估计中耳效率。在15名听力正常的受试者的两个探头位置进行了ZEC的声学测量。ZEC对测量位置敏感，尤其是在耳道共振和反共振频率附近。将ZEC转换为ZED可减少耳道的影响，与ZEC相比，在1至12kHz之间降低了ZED的插入深度敏感性。吸收率A对探头位置的敏感性低于ZEC，但在5kHz以上比ZED更敏感。在1至5kHz之间，ZED和A对探头位置的敏感性相似。1kHz以下ZED的探头位置敏感性与A或ZEC相比没有降低。中耳效率呈带通形状，在1至4kHz之间效率最高。ZED和中耳效率的估计可以扩展宽带声导抗测量的诊断能力。
