MECHANICAL CHARACTERISTICS AND SOUNDING MECHANISM OF SOUNDING MEMBRANE IN BLACK CICADA(C. atrata Fabricius)

Abstract

In this paper, the geometric structure and the mechanical characteristics of the sounding membrane (SM) are given, and the acting properties of the sounding movement of sM are revealed.SM is an elastic membrane with a non-linear structure. At contracting point, the elastic pressure and the rebounding force are about 0.146 N and 0.044 N, respectively. In the lower half, the rigidity of the convex-like shell increases obviously, its force constant is about 0.4 N/ram. In the upper half, the middle section of the three long ribs narrows, thickens and stiffens, with a breaking pressure of about 0.12N.The forced sounding movement of SM shows that the movement of SM travels along the membrane in the lower half from the contracting point and drives the three long ribs to buckle in turn and to produce a syllable to be basically the same as free song, that is, it consists of the three amplitude-modulation pulse trains of which the main peak frequency of the carrier wave is about 4.8 kHz. The buckling movement of the long ribs presents an unstable property like a frangibilio-elastic body. The critical driving force and the increment of driving force in the instability are about 0.04 N and 0.0094 N, respectively, and the force constant suddenly drops to about 0.017 N/mm.