For many recording facilities, the isolation of floor-borne noises from room and building exteriors is an important consideration. For example, a building that’s located on a busy street and whose concrete floor is tied to the building’s ground foundation might experience severe low-frequency rumble from nearby traffic. Alternatively, a second-floor facility might experience undue leakage from a noisy downstairs neighbor or, more likely, might interfere with a quieter neighbor’s business. In each of these situations, increasing the isolation to reduce floor-borne leakage and/or transmission is essential. One of the most common ways to isolate floor-related noise is to construct a “floating” floor that is structurally decoupled from its subfloor foundation.
Common construction methods for floating a professional facility’s floor uses either neoprene “hockey puck” isolation mounts, U-Boat floor floaters (Figure 3.9), or a continuous underlay, such as a rubberized floor mat. In these cases, the underlay is spread over the existing floor foundation and then covered with an overlaid plywood floor structure. In more extreme situations, this superstructure could be covered with reinforcing wire mesh and finally topped with a 4-inch layer of concrete (Figure 3.10). In either case, the isolated floor is then ready for carpeting, wood finishing, painting or any other desired surface.
An even more cost- and space-effective way to decouple a floor involves layering the original floor with a rubberized or carpet foam pad. A 1/2- or 5/8-inch layer of tongue-and-groove plywood or oriented strand board (OSB) is then laid on top of the pad. These should not be nailed to the subfloor; instead, they can be stabilized by glue or by locking the pieces together with thin, metal braces. Another foam pad can then be laid over this structure and topped with carpeting or any other desired finishing material (Figure 3.11).
It is important for the floating superstructure to be isolated from both the under-flooring and the outer wall. Failing to isolate these allows floor-borne sounds to be transmitted through the walls to the subfloor, and vice versa (often defeating the whole purpose of floating the floor). These wall perimeter isolation gaps can be sealed with pliable decoupling materials such as widths of soft mineral fiberboard, neoprene, silicone or other pliable materials.
Excerpt from Modern Recording Techniques, 8th Edition by David Miles Huber and Robert E. Runstein © 2013 Taylor & Francis Group. All Rights Reserved.