Constrained Layer Damping Construction
Back to wall shudder. Stick frame constructed walls, floors and ceilings comprise the bulk of how listening rooms and home recording studios are constructed. Sheetrock is heavy and studs are stiff and this combination of weight and stiffness results in wall twang, a natural resonant frequency, which is easily stimulated by the subwoofer. The critical listener hears the direct sound accompanied by various arrangements of room acoustics and structural shudder. We had calmed room acoustics but now needed to put the brakes on the sympathetic shudder of the surfaces of the playback room and for that we turned to the world of CLD, constrained layer damping.
Constrained layer damping was not and still isn’t typically usually used in residential or commercial construction but it is commonly used in the construction of ships, boats, trains, planes and RVs. All these vehicles experience severe structural vibration issues, caused usually by their prime motors, and they all need to provide a calm and comfortable ride for the paying passengers. These vehicles are not grounded and the vibration has no opportunity to be resisted by the mass of the ground. Their only solution to runaway vibration is constrained layer damping. We applied this type of construction technique in the DIY type audiophile listening rooms and recording studio projects we were working on and were very pleased to discover how well it worked.
We researched and found an excellent viscoelastic constrained layer damping material used in the manufacturing sector, acquired exclusive rights to process and sell it in the public domain, and we named it ASC WallDamp. This was back in 1987 and remains still so today. WallDamp is a 1mm thick sheet of damping compound covered with self stick adhesive and release paper. In basic wall construction projects you apply WD Strips to the face of the studs and wall plates and then screw the sheetrock down. The first benefit you hear is that the sheetrock stops vibrating between the stud. That familiar hollow sheetrock sound you hear when you knock on the wall with your knuckle, goes away.
 The second benefit you hear is that the lower frequency shudder from the sheetrock/stud vibration also goes away. It’s that thummm sound you hear when you double up your fist and thump the middle of the wall, halfway up from the floor. WallDamp strips applied to the face of the stud, blocking and upper and lower plates makes all the difference between noisy walls and calm walls. And don’t forget, while that damping compound is calming the walls, it’s also turning the walls into giant CLD membrane bass traps which absorbs deep bass out of the room.
If a second layer of sheetrock is applied over the first layer, add WallDamp squares on 9 to 12” centers and WD Strips around the perimeter to the face of the first layer of sheetrock. Screw the second layer of sheetrock down normally. The result is an even more calm walls, floor and ceiling which means we are helping people make better sounding rooms, long before they ever put sound panels or bass traps into the rooms.
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