Generally recommended soundproof doors are generally filled with sound-absorbing cotton or PU inside, and some simply use cardboard to partition into a so-called honeycomb structure. On the one hand, the strength of the door panel is increased to a certain extent by the closed air layer formed on the one hand. Soundproofing. Basically, any material has its sound-insulating effect, and simply speaking, the heavier the object is, the better its sound insulation is. This is the so-called quality rule, which means that you can use a 4cm thick rigid plate for sound insulation. For door panels or cement in the door panels to improve quality for higher sound insulation, but the sound insulation effect is achieved but the weight of the door panels does increase the burden on the door hinge, if the hinge can not fully load the door leaf will not be easy The switch even causes damage to the hinge, so unless necessary, the weight of the soundproof door will be reduced as much as possible to achieve the desired sound insulation.