What does Resonator mean?
Trapped air volume in a container (which upon excitation makes a sound; for example, blowing across a bottle mouth). This forms a resonator. The air in the cavity is like a coiled spring and the mass of the air in the neck of the bottle reacts with this property to form a resonating system. The sound so produced has a frequency characteristic of the air volume, diameter of the mouth and length of the neck of the resonator. Change any one of these, and the frequency of the emitted sound changes.