Stinson M R, Khanna S M
Institute for Microstructural Sciences, National Research Council, Ottawa, Ontario, Canada.
J Acoust Soc Am. 1994 Jul;96(1):170-80. doi: 10.1121/1.410461.
Spatial pressure distributions have been measured in the ear canals of ten cats and analyzed to obtain the energy reflection properties of the middle ear over a 10- to 25-kHz range of frequencies. Considerable intersubject variability is observed, much of which can be correlated with the condition of the tympanic membrane. For ears judged to be in good condition, reflection coefficients typically take values of about 0.2 between 15 and 25 kHz, indicating good matching of the dynamical properties of the auditory system to the ear canal sound field. At lower frequencies, the reflection coefficients tend to be somewhat higher and at higher frequencies the reflection coefficients increase quite rapidly with frequency. For ears judged to be in poorer condition, energy reflection coefficients of 0.5 and 0.9 were determined for the 15- to 25-kHz range. The variations of sound pressure along the canal (about 10 dB, even in well-coupled systems) confirm that single point pressure measurements may be inappropriate for defining the acoustical input at higher frequencies and new measures for specifying the input should be investigated. The net flow of acoustic energy into the auditory system, the sound power, is one possibility. Some initial measurements of sound power, obtained from analysis of the spatial pressure distributions, are presented.
已对10只猫的耳道内的空间压力分布进行了测量，并进行分析以获得中耳在10至25千赫频率范围内的能量反射特性。观察到个体间存在相当大的变异性，其中大部分可与鼓膜的状况相关联。对于判断为状况良好的耳朵，在15至25千赫之间，反射系数通常取值约为0.2，这表明听觉系统的动态特性与耳道声场匹配良好。在较低频率下，反射系数往往略高，而在较高频率下，反射系数随频率迅速增加。对于判断为状况较差的耳朵，在15至25千赫范围内确定的能量反射系数为0.5和0.9。沿耳道的声压变化（即使在耦合良好的系统中也约为10分贝）证实，单点压力测量可能不适用于定义较高频率下的声学输入，应研究用于指定输入的新方法。进入听觉系统的声能净流量，即声功率，是一种可能性。本文给出了通过对空间压力分布进行分析获得的一些声功率初步测量结果。
