Sound insulation board is usually used when the wall itself can’t block enough noise. The room to the room noise insulation is rated by sound transmission level (STC). The acoustic properties of ordinary walls are usually STC 30 to 34. This is considered poor because you can easily hear the conversation.
Mass loaded vinyl is a new thin insulation board or method of improving wall isolation which blocks about 26dB independently. Many customers ask if they add this MLV can they get 30 + 26 = 56 dB? The answer is no. To understand this, you need to know more about how insulation board works.
Adding mass to the walls follows the law of mass, where the specified wall mass is doubled and an increase of about 5 to 6 dB can be reached. That is, the mass of the whole structure doubles!
Noise can be reduced by additional mass, and MLV weighing about 4 kg/m2. For this type of acoustic treatment, the mass of the material is the main factor. However, before adding a large amount of MLV or EPDM insulation board, the walls have already weighed 20 kg/m2, so the extra pounds added by the single layer of vinyl are only a small amount of added mass, not even doubled.
Another reason, MLV is not the finish board. Let’s take gypsum board as finish board for example.
One main way of sound propagation is to pass through the stud rather than the air in the cavity. The addition of the vinyl layer hardly changes this because the outer gypsum will be pushed into or directly screwed into the stud through the vinyl thread. For significant improvement, the path must be fundamentally changed, or specific damping can be introduced in the structure. Gypsum board is not waterproof, we recommend use MgO soundproof boards or soundproof panels instead.
So the installation of MLV and other acoustic insulation board is important. MLV is installed on wood batten and sealed. Gypsum wall insulation board is installed on MLV but the studs head are on MLV rather than wood batten. MLV is also a damping material which reduce the sound passing through studs. Together, they make a good insulation system.