It is widely used in the design of metal ceilings to reduce noise and create a comfortable space. The addition of sound insulation paper or sound insulation on the back of the perforated smallpox can help increase the total absorption capacity of the whole closed space and reduce the effect of noise. Each perforation from can provide different absorption open area ratio (punching rate), to achieve different degree of closed space absorption demand. There are many kinds of punch forms that are not recorded, and different types of punch patterns are available for customer selection.