The Noisy Cicada
The cicada is a noisy insect. It produces ticks, buzzes and whines by means of a system in its body. There is a pair of membranous organs at the base of the insect's abdomen. The cicada produces that well-known sound by vibrating these drum-like membranes. When these membranes are pulled and released by the muscles to which they are attached, a sound similar to that of an empty tin is produced. The insect repeats this pull-and-release process 500 times a second. Considering that you can only close and reopen your eyes once in a second, you can readily see how difficult it is to perform this task 500 times a second.
With the opening and closing of the extended part that exists on the lower part of the insect's thorax, the sound level may be increased or decreased. The human ear cannot perceive these openings and closings, which occur in a tenth of a second, so we do not notice that the sound is interrupted and we think that the buzzing song of the cicada is continuous.