ASC develops Stud Stabilizer 1 and 2, an inertia based vibration damping system for Wall Studs and Floor Joists

The stud stabilizer is an inertial stabilizer device. Whenever the pivot end of the stabilizer is accelerated perpendicular to the length of the pendulum arm, the pendulum weight lags behind the movement of the pivot end. This causes a rotation action around the pendulum pivot pin. The pendulum pivot is surrounded with a set of friction plates which absorbs energy out of the rotation.

The pivot point of the stud stabilizer pendulum is connected to the mid point of a wall stud. When the stud vibrates, the midpoint of the stud swings back and forth and drags the pivot of the pendulum back and forth. The hanging weight of the pendulum is about 3’ below the pivot point and it tends to not move so easily. It requires rotational inertia to be transferred from the stud to the hanging pendulum in order to get it to move. This torque transfer is achieved by adding WallDamp material between the stud and the pendulum arm of the StudStablizer. This torque produces sheet stress in the WallDamp compound which is converted into friction and the rapid damping of the stud vibration.

When studs are used to support floating walls, typically used in soundproofing projects, the studs are often not connected to any structure. When this is the case the small vibrations of the wall surface are transmitted to the supporting stud through the springs, the resilient channels or rubber mounting clips. At certain frequencies the stud is stimulated into resonance. While this may be of minor consequence in general construction, in high power audio playback rooms, it can be a major problem.

High performance audio rooms are so quiet inside and so acoustically fast in response that as the music plays, sounds and tones come and go quickly. When a tone slightly shakes the floating wall, which happens to be the same frequency as the resonance of the supporting stud, the stud is stimulated onto movement. When the musical moment stops, the listener continues to hear an odd sound, the sound of the stud vibrating behind the wall. This kind of sonic afterglow is unacceptable in high performance rooms.

Another circumstance where stud vibration becomes a problem is when the suspended wall is connected to a set of studs that has sheetrock on the other side. This sheetrock and stud wall also has a natural resonance which can be stimulated by the movement of the floating wall. The interior wall vibration can become so great that things attached to the wall will rattle, which even further degrades the results of the sound isolation project.

When freely vibrating studs are used to support a floating wall, either damping or a rigid connection can be used to keep the stud from vibrating. Sometimes it is possible to cross brace the middle of a stud, or to connect it to a nearby concrete wall, and keep it from vibrating. However, frequently the situation is that there is no way to support the free standing stud and damping it’s free vibration is the only option.

ASC has also developed inertial stabilizers for floor joists. The principles are the same except that a double pendulum system is used, with both being laid horizontal instead of a single unit hanging vertical.

Contact ASC engineering if you have other vibration management applications that might benefit from inertial damping. Inertial damping does not rely on being cross braced to other points in the structure, it depends only upon the acceleration of the point to which it is attached.

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