TRANSMISSION CHARACTERISTICS 



273 



Transmission Characteristic of the Malleus-Incus Articula- 

 tion 



It was shown by Stuhlman [1937] that the malleus-incus articulation 

 functioned as an asymmetrical non-linear transmission mechanism ex- 

 cept for very small displacements. He constructed an accurate 20-to-l 

 scale model of theossicles so thattheir rather complicated relative motions 



Fig. VII-11. Experimental transmission characteristics of the malleus-incus 

 coupling obtained from a 20 X model. Shift of the operating point of the charac- 

 teristics from A to C shows increased coupling. The linear characteristic D indicates 

 rigid coupling. The typical basic operating curve for the malleus-incus articulation 

 is sigmoid shaped, as A, where the dotted line shows unstable condition attained as a 

 result of a slight dislocation when force directed inward becomes too large. (Stuhl- 

 man [1937].) 



could be analyzed. Within the limitations set by the model in simulat- 

 ing the correct suspensions and articulations, it was found that, when a 

 simple vibratory motion was impressed at the end of the lever arm of 

 the malleus, it was transmitted to the end of the long crus (lenticula 

 process) of the incus after having undergone both asymmetrical and 

 non-linear distortion on passing through the malleus-incus articulation. 

 A characteristic family of transmission curves for various degrees of 

 coupling of the malleus-incus articulation is shown in Fig. VII-11. The 

 basic curve A is sigmoidal in shape. The upper branch, because of 



