Ravicz M E, Rosowski J J
Eaton-Peabody Laboratory of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston 02114, USA.
J Acoust Soc Am. 1997 Apr;101(4):2135-47. doi: 10.1121/1.418275.
The effects of variations in middle-ear cavity size on hearing sensitivity in the Mongolian gerbil are predicted by computing the effect on acoustic power input to the middle ear. Acoustic power collection from a diffuse sound field was computed from measurements of the middle-ear input impedance and external-ear radiation impedance and mathematical models of the middle and external ear presented in the first two papers of this series [J. Acoust. Soc. Am. 92, 157-177 (1992); J. Acoust. Soc. Am. 99, 3044-3063 (1996)]. A reduction in middle-ear cavity volume to 1/4 its normal value is predicted to cause a frequency-selective elevation in auditory threshold of as much as 12 dB, with the largest elevation occurring in the 1-2 kHz range. Greater reductions produce larger threshold elevations. Increases in cavity volume cause decreases in the predicted threshold of at most 12 dB. Threshold predictions for volumes equal to those of the smaller hamster and the larger kangaroo-rat middle-ear cavity volumes resemble threshold functions measured in those animals. Results are consistent with the idea that large middle-ear cavities evolved in gerbil to improve hearing sensitivity below 3 kHz and thereby improve the animal's chances for survival.
通过计算中耳腔大小变化对输入中耳的声功率的影响，预测其对蒙古沙鼠听力敏感度的影响。根据本系列前两篇论文[《美国声学学会杂志》92, 157 - 177 (1992); 《美国声学学会杂志》99, 3044 - 3063 (1996)]中给出的中耳输入阻抗、外耳辐射阻抗测量值以及中耳和外耳的数学模型，计算从扩散声场收集的声功率。预计中耳腔体积减小至正常体积的1/4会导致听觉阈值出现频率选择性升高，最高可达12 dB，最大升高出现在1 - 2 kHz范围内。更大程度的减小会导致更大的阈值升高。腔体积增加会使预测阈值最多降低12 dB。与较小仓鼠和较大更格卢鼠中耳腔体积相等时的阈值预测类似于在这些动物中测量的阈值函数。结果与以下观点一致：沙鼠进化出大的中耳腔是为了提高3 kHz以下的听力敏感度，从而增加动物的生存机会。
