Acoustic board

An acoustic board is a special kind of board made of sound absorbing materials. Its job is to provide sound insulation. Between two outer walls sound absorbing material is inserted and the wall is porous. Thus, when sound passes through an acoustic board, the intensity of sound is decreased. The loss of sound energy is balanced by producing heat energy.
Uses.
They are used in auditoriums, halls, seminar rooms, libraries, courts and wherever sound insulation is needed. Acoustic boards are also used in speaker boxes.
References.
Acoustic Board