Q:
We live in a condominium and have a garage-door noise problem. Our bedroom is immediately above the neighbor’s garage. When our neighbor arrives home late at night and opens the overhead garage door, the automatic-door motor frightens us out of our sleep.
Robert D. Michael, Sunnyvale, CA
A:
Tom Rose, an acoustical consultant in Flower Mound, Texas, replies: Noise from an operating garage door that’s heard in the space above the garage is structure-borne noise. The building is transmitting vibrations generated by both the garage-door motor and the door track. Structure-borne noise is different from the more-common condo and apartment noise problem, airborne noise, which can be heard through walls.
Airborne-noise problems can be mitigated with insulation in walls or with acoustical panels placed on wall surfaces. With a structure-borne noise problem, you must break the rigid tie between the vibrating elements and the building structure. In this case you should remount the garage-door track and the door opener on rubber vibration isolators. Two manufactures of vibration isolators are Kinetics Noise Control (6300 Irelan Place, Dublin, Ohio 43017; 614-889-0480) and Mason Industries (P.O. Box 410, Smithtown, N.Y. 11787; 516-348-0282). Use a Kinetics model RCA or a Mason model ND-A.
The isolators are available in a range of load capacities and should be sized to carry the weight of the door in the open position. These isolators must not be loaded in tension; in other words, you can’t hang something from them. But they can be loaded in shear: mounted sideways where loads are low, such as where the track attaches to the wall. For the ceiling support of the main loads, the isolators should be loaded in compression (see drawing).
There is a threaded insert in the top of the isolators. When you fasten the door hardware to the isolator, use a bolt that’s long enough to engage the threaded insert but that doesn’t extend past the center of the isolator. If the bolt touches the bottom, the bolt will transmit the vibrations and render useless the rubber vibration isolator.
