Test and analysis: (1) Objects can be identified by timbre. Different generator materials and structures will produce different timbres. We identify different vocal bodies by timbre. Because cicadas and birds have different vocal bodies, we can distinguish cicadas from birds by their different timbres.

(2) Many experiments and common sense of life tell us that sound is produced by vibration; Once the vibration stops, the object can't make a sound. For example, "the clock doesn't ring" means that the object can only make a sound when it vibrates.