Can Cement Drywall Help Soundproof a Room?

How Sound Travels

• Sound travels by vibrations. Sound is vibrations of the air. These vibrations travel to your ear, where they vibrate the ear drum. The vibrations send a signal to your brain, which translates the vibrations into understood sounds. When sound waves hit an object, they can be absorbed or reflected. When an object absorbs sounds, it deadens the sound; but if it reflects the sound, you hear an echo. Sounds can travel along objects such as the wood frame of a house. Heavy stomping on an upper floor of a house can vibrate the wood frame throughout the house, so someone in the basement can hear the stomping.

Soundproofing

• Soundproofing combines sound-absorbent wall materials such as drywall with sound barriers or baffles inside the walls such as insulation. A total soundproofing system should consider both the covering over the walls and the material inside the walls. Caulk around the edges of the cement drywall after insulating it to keep sound and air from seeping into the room.

Behind the Cement Drywall

• The material inside a wall matters as much as the surface cement drywall for soundproofing. The top and bottom supports for the wall frame should be wider than traditional 2-by-4 studs. A 6-inch-wide top and bottom support for the frame with 2-by-4 studs lets you put each stud flush with an opposite side of the support -- so one stud would be closer to the inside wall and the next would be closer to the outside wall. Set studs every 8 inches measured between the center of each stud. Wrap insulation around air ducts and pipes in the walls, and fill the remaining space in the walls with batting insulation.

Cement Drywall

• The material you choose will greatly determine how much sound it absorbs. A greater amount of absorption, measured by the noise reduction coefficient, will create a quieter room. Cement drywall differs from traditional gypsum drywall in its material and construction, in its soundproofing qualities and in its moisture resistance. Gypsum drywall that's 1/2 inch thick has a noise reduction coefficient (NRC) of 0.16, which is higher than that of plywood paneling, according to "Creative Homeowner's Ultimate Guide to Home Repair and Improvement: 325 Step-By-Step Projects." Tests conducted by the Civil Engineering Research Foundation and published in "An Evaluation of Laboratory Test Results for the U.S. Gypsum Sight and Sound Screen System" found that the NRC of 1/2-inch-thick cement board was similar to that of gypsum drywall at 0.15. The advantage cement drywall has over gypsum drywall is its water resistance, so it can be used in bathrooms.