Lees S, Hanson D B, Page E A
Bioengineering Department, Forsyth Dental Center, Boston, Massachusetts 02115, USA.
J Acoust Soc Am. 1996 Apr;99(4 Pt 1):2421-7. doi: 10.1121/1.415430.
The otic bones in this report are the tympanic bulla, the periotic, and the three ossicles (malleus, incus, and stapes) of an adult fin whale (Balaenoptera physalus). The purpose was to determine if the periotic was denser than the other otic bones. It was found in one male adult fin whale that the density of all the otic bones is approximately the same, 2.50 kg/m3 with a maximum of 2.58. The lowest density was observed in the stapes (2.36). The sonic velocity seems to vary as the density but there also seems to be a structural effect. The maximum sonic velocity was 4.89 km/s in the malleus. The specific acoustic impedance was as high as 12.5 megarayles in the periotic. These values compare with those for human femur of 1.95 for the density, 3.73 for the sonic velocity, and 7.33 for the specific acoustic impedance. The ossicles weigh as much as 200 times as much as human ossicles. The density of whale ossicles are about ten percent greater than human ossicles. The mechanical natural frequency of the whale ossicles must be very low. The approximate uniformity of the properties of this whale's otic bones may be characteristic of the middle ear. The density of the otic bones of land mammals is less than for whales. The density of the horse petrosal (2.29 g/cc) is essentially the same as the density of adult human ossicles (2.23-2.27 g/cc). The high density of the otic bones for all mammals suggests it may be related to hearing acuity perhaps by increasing the specific acoustic impedance, which increases the acoustic contrast with the other body tissues.
本报告中的耳骨包括成年长须鲸（Balaenoptera physalus）的鼓泡、围耳骨以及三块听小骨（锤骨、砧骨和镫骨）。目的是确定围耳骨是否比其他耳骨密度更大。在一头成年雄性长须鲸中发现，所有耳骨的密度大致相同，为2.50千克/立方米，最大值为2.58。镫骨的密度最低（2.36）。声速似乎随密度变化，但似乎也存在结构效应。锤骨中的最大声速为4.89千米/秒。围耳骨的比声阻抗高达12.5兆瑞利。这些值与人类股骨的值相比，密度为1.95，声速为3.73，比声阻抗为7.33。鲸的听小骨重量是人类听小骨的200倍之多。鲸听小骨的密度比人类听小骨大约高10%。鲸听小骨的机械固有频率必定非常低。这种鲸耳骨特性的近似均匀性可能是中耳的特征。陆地哺乳动物耳骨的密度低于鲸类。马岩部的密度（2.29克/立方厘米）与成年人类听小骨的密度（约2.23 - 2.27克/立方厘米）基本相同。所有哺乳动物耳骨的高密度表明，这可能与听力敏锐度有关，或许是通过增加比声阻抗来实现的，比声阻抗的增加会增强与身体其他组织的声学对比度。
