I believe many people have seen people play beautiful sounds with glasses full of water. Even many people try to make clear and pleasant sounds themselves. Few people know why they make such beautiful sounds. So, what causes this sound?
When you flick the glass with your fingers, the edge of the glass mouth will vibrate. This vibration matches the vibration easily generated by glass, and the vibration will become larger and larger, producing sound. However, it should be noted that when the double-layer glass vibrates and sounds, it will prevent cracking. The reason for the cracking is that once the hot water enters the expansion cup, the inner wall of the glass will expand rapidly, but the outer wall remains unchanged, and the inner cup will be suddenly squeezed outward, resulting in the cracking of the glass. As long as the inside and outside of the cup are heated at the same time in advance, and then the hot water is poured into the cup, the expansion degree inside and outside the cup will not be so large, and then tapping the cup will not explode.