Willi Urban B, Ferrazzini Mattia A, Huber Alex M
Laboratory of Experimental Audiology, Department of Otorhinolaryngology, University Hospital of Zürich, Frauenklinikstrasse 24, 8091, Zürich, Switzerland.
Hear Res. 2002 Dec;174(1-2):32-44. doi: 10.1016/s0378-5955(02)00632-9.
The question as to whether the incudo-malleolar joint (IMJ) is mobile or immobile at moderate sound pressure levels (SPLs) is addressed. Referring to the mechanical properties of elastic tissue, we suggest that the IMJ is mobile at any SPL. In order to test this hypothesis, we investigated the dynamics of the IMJ in nine temporal bones by means of laser scanning doppler vibrometry. The dynamic behavior of both ossicles, malleus and incus is described by three degrees of freedom, and transfer functions (TFs) are shown for each motion component [corrected]. We show that there is indeed relative motion between the malleus and the incus. This transmission loss affects the middle ear TF and results in a frequency dependent sound transmission loss. Some characteristics of our results are in agreement with middle ear TFs described in the literature. The increasing transmission loss towards higher frequencies is caused by relative motion between malleus and incus at the IMJ. The concept that the IMJ is functionally mobile is consistent with the physical properties of elastic tissues which most likely define the mechanics of this joint. Since the IMJ is indeed mobile at moderate sound intensities and audible frequencies the theory of the lever ratio being responsible for the characteristics of the middle ear TF must be reconsidered.
本文探讨了在中等声压级（SPL）下，砧镫关节（IMJ）是可移动的还是固定不动的问题。根据弹性组织的力学特性，我们认为IMJ在任何声压级下都是可移动的。为了验证这一假设，我们通过激光扫描多普勒振动测量法研究了9块颞骨中IMJ的动力学特性。锤骨和砧骨这两块听小骨的动态行为由三个自由度来描述，并给出了每个运动分量的传递函数（TF）[已校正]。我们发现锤骨和砧骨之间确实存在相对运动。这种传输损耗会影响中耳TF，并导致与频率相关的声音传输损耗。我们的一些研究结果与文献中描述的中耳TF一致。向高频方向传输损耗增加是由IMJ处锤骨和砧骨之间的相对运动引起的。IMJ在功能上是可移动的这一概念与弹性组织的物理特性相符，而弹性组织很可能决定了该关节的力学特性。由于IMJ在中等声强和可听频率下确实是可移动的，因此必须重新考虑杠杆比决定中耳TF特性的理论。
