(2) When the sound reaches the surface of an object, part of the sound is reflected by the surface of the object and the other part is absorbed by the object, so we can choose the silencing material from these two functions;
(3) In order to study which material has better sound insulation performance, it is necessary to control variables to control the thickness and shape of cotton cloth and ceramic tile.
Cotton cloth and ceramic tiles with the same thickness can be made into boxes with the same volume and shape, and a small alarm clock (or other objects that can make sounds) can be put inside. People can judge which object has good sound insulation effect according to the sound they hear outside.
(4) Control noise to reduce noise in three ways: at the sound source, in the process of propagation, and at the human ear, for example, don't turn up the volume of TV and stereo at night; Don't chase and fight in the classroom between classes; Don't let the desks and chairs ring in class.
So the answer is: (1) eyes;
(2) reflecting sound; Absorb sound;
(3) Experimental equipment: cotton cloth, porcelain, small alarm clock;
Experimental steps: make cotton cloth and porcelain pieces with the same volume and shape, and put a small alarm clock (or other objects that can make sound) inside to make it make sound. People can judge which object has good sound insulation effect according to the sound they hear outside.
(4)① Don't turn on the loud stereo in the middle of the night; Don't shake tables and chairs casually to make noise in class.