Decay of amplitude modulation property of song and an analysis of sounding mechanism in mottled cicada(Gaeana maculata Drury)

In the natural song of the mottled cicada, the prelude and loud song of the prologue and the repetition consist separately of trains of pulses, each containing three subpulses(SP_1-3).
The principal frequencies(PF_b and PF_c) of the basic sound and carrier frequeency band are 338+20Hz and 3617+87Hz,respectively.The prelude of the prologue contains 22 pulses(P_1-22) whose amplitude modulation properties gradually decay. The carrier wave oscillation gradually loses its positive negative symmetry and superimposes with the basic waves of the SP₁. The SP_2,3 are essentially sinusoidal. Moreover, the song with the PF_c as the dominant tone gradually gives way to the PF_b. In the loud song of the prologue the prelude and the loud song of repetition, the amplitude modulation properties are further lost. The carrier wave oscillation mainly superimposes with the basic waves of the SP₂, all the amplitudes of PF_c being over 10 dB lower than those of the PF_b and the latter playing as the dominant tone of the song.In view of the sturcture of the sounding membrane, the vibration frequentes of the three long ribs may be gradually changed from mass controlled to mechanical-resistance controlled. In correspondence the PF_c as the dominant tone is gradally taken over by the loud song and repetition with the PF_b as the dominant tone.
In view of the sturcture of the sounding membrane, the vibration frequencies of the three long ribs may be gradually changed from mass controlled to mechanical-resistance controlled. In correspondence the PF_c as the dominant tone is gradally taken over by the loud song and repetition with the PF_b as the dominant tone.