With multifamily construction leading the charge of development over the past several years acoustic issues have only become more prevalent to developers, designers and tenants alike. Everyone in the industry is constantly searching for a “magic bullet” product.
The problem is that this “magic bullet” simply doesn’t exist. Noise in multifamily is a system approach, meaning that every component in either the floor/ceiling or wall assembly is crucial to the overall performance, including resilient channels. Some elements are more effective limiting the transfer of airborne and impact noise but in many circumstances building practices used have a huge effect of how the system will ultimately perform. As the technology of noise control products continue to improve, as well as their stated effectiveness, we cannot forget that quality control and attention to detail is still the most crucial step to limiting noise transfer.
Mass and Isolation
In acoustics there are two primary functions that limit the two types of noises we are concerned with: mass and isolation.
Mass is a relatively simple application and easier method to understand. The more mass a wall or floor/ceiling component has, typically the better job that part of the assembly will do at limiting airborne noise passage through it. Acoustically enhanced drywall and cementitious floor underlayments are prime examples of this theory. Both products contain much more mass than the alternatives (standard drywall or no cementitious leveler used) and the airborne transfer or sound transmission class of that assembly is positively affected.
Isolation is slightly more difficult to understand, as well as properly accomplish. Creating isolation between the different layers of the wall or floor/ceiling assembly help to greatly reduce vibration transfer. By reducing vibrational transfer we greatly increase the ability for the assembly to limit the amount of impact noise that can pass through, thus creating quieter living spaces. With the biggest complaint in multifamily construction typically coming from “stomping noises” heard from units above it’s easy to see how critical this detail might be. Through the use of resilient channels and acoustical underlayments, designers are attempting to limit the connectivity of these systems to quell these issues. Even when properly designed many times these systems unfortunately do not perform up to their capabilities through a few common installation errors.
One commonly incorrect installation lies within the attachment of the gypsum board ceiling to the resilient channels. These systems are designed to use a 1-inch screw to attach the two, but commonly in the field installers will use longer screws because of the time saving and ease of installation. They may say, “A 1½-inch screw and a 1-inch screw should do the same thing, right?” Wrong. The longer screws used have the length to pass through the plate of the resilient channel and attach into the bottom of the joist, creating a short circuit in the system. These short circuits allow for additional paths for vibration to travel resulting in lower Impact Insulation Class ratings for the entire system.
Innovation for the Future
Recently, manufacturers have taken on this problem through added innovation. In acoustics, it’s clear that even the best systems have problems when the proper installation details are not followed. Manufacturers of late have stepped up to the plate to help quell this difficult issue through some unique innovations. With that being said, there is no substitute for good old fashion craftsmanship and extra precaution to help limit noise transfer. With the continued trend of increasing shared living space, these issues will continue to manifest themselves until the construction community raises its level of expectation from those who are building our future communities.