Maxx Minutes Blog

Proper Acoustical Construction - A Discussion of Sound Control Components in Multifamily Floor/Ceiling Assemblies

In today’s multifamily construction market, upgraded sound control is giving savvy developers the edge over penny pinching competition. An increased focus on amenity based rental experiences are leading residents to also demand better sound control as part of their renting experience. While underlayments and sound control mats make a difference in overall noise reduction, they represent only two elements of the sound control equation. Upgraded sound control is achieved by also considering all other assembly components and proper installation techniques.
To ensure that the benefits gained through a properly installed sound control system are not adversely impacted by the floor/ceiling assembly, it is important to understand each component and its potential sound control implications.
Addressing Assembly Components

  • Assembly Type and Subfloor – According to the Mass Law, the greater the mass, the greater the sound energy (sound wave) required to transmit through it, therefore a thicker assembly will provide greater sound reduction.  The stiffness of the assembly also matters as a stiffer floor will reflect more sound.
  • Insulation – Fiberglass insulation provides sound absorption in the joist spaces which helps absorb sound waves as they pass through the system.  Sound absorptive material is very important within the joist cavity, however there is a law of diminishing returns. In other words, doubling the thickness of insulation will not double the degree of improvement realized from the initial thickness.
  • Decoupling
    • Resilient Channel – Resilient channel effectively de-couples the ceiling from the joists therefore creating a vibration break. It is important to note that not all resilient channels are created equal.  Maxxon has observed that channel in the 0.017"–0.022" thickness (25-27 gauge) range with repetitive 4" long slots and 1⁄2" separations performs the best. Heavier gauge does not constitute better acoustical performance.
    • Hangers – There are now products on the market that can be used to hang a resilient ceiling, thus addressing flanking issues that come with poor installation. The products come in the form of rubber clips and spring systems and many have proven to perform as well as good quality, well installed resilient channel.  Make sure to thoroughly evaluate the sound test reports for these products or call Maxxon for further thoughts on this topic.

Note: The combination of decoupling with insulation is very effective in noise reduction; however one without the other is not nearly as efficient.

  • Gypsum Board – Gypsum board is also significant as it completes the cavity, resulting in a “dead air” space within the truss cavity. Dead air is an effective method of increasing STC and IIC performance, and is further enhanced by the inclusion of fiberglass insulation. Additionally, the gypsum board provides a dead load which is necessary for the resilient channel to work properly and further increases the mass of the system.

Beyond sound control, assembly design is also imperative to achieving a specific UL Fire Rating. Because both aspects are essential in the multifamily housing industry, an emerging trend is the issuance of evaluation reports by reputable third party organizations. Evaluation reports prequalify all support testing for sound and fire for specific assemblies in one document, which ensures that a specific, well-built design will achieve or exceed fire and sound code.
Flanking Paths

In order for assembly components to perform effectively, it is necessary to eliminate flanking paths that allow sound to circumvent these components. The term “flanking paths” refers to any sound path around the building element. The potential for flanking paths is significantly reduced in several ways:

  • Proper floor/ceiling isolation – achieved by resiliently mounting gypsum board so that it does not have direct contact with the joist or wall.
  • Correct installation of assembly components.
  • Isolation of potential flanking paths, like wall/floor junctions, prior to installation of a sound control system.

 

Update on Sound Control Guidelines

The International Building Code requires a minimum IIC and STC of 50, however many developers are realizing the value of a sound control system that performs above code minimum. Properties with well-designed sound control systems are seeing higher fill rates and reduced tenant turnover. These properties are also proving to hold their values and sell faster. Therefore, the International Code Council, authors of the International Building Code, has issued an appendix to the code called ICC G2-2010 Guideline for Acoustics. This guideline establishes two additional levels of acoustical performance above code minimum:

  • ‘Acceptable’ Performance – 55 STC/IIC
  • ‘Preferred’ Performance – 60 STC/IIC

These higher ratings are achieved through the addition of a well-designed sound control system comprised of two elements, a sound control mat and an underlayment. The addition of a sound control mat helps to control impact borne (IIC) sound waves, like footfall or objects being dropped, while an underlayment will help to reduce airborne (STC) sound waves, such as voices and clapping, and is imperative in achieving a UL Fire Rating for the floor/ceiling assembly.  It is commonly accepted that the thicker a sound control mat, the better the IIC reduction, however Maxxon recommends comparing sound control data when selecting a sound control system to verify expected results.

Product Update

Maxxon Corporation offers ten levels of sound control solutions. To help identify the right solution for your next project, Maxxon offers a variety of helpful tools. The Interactive System Selector located on our website makes it easy to quickly identify noise deadening options that fall within the scope of your project. When you are ready to match and document a specific level of sound deadening with a UL Fire Design, Maxxon offers the Fire and Sound Manual, which matches our 100+ UL Fire Rated Designs to corresponding floor/ceiling assemblies and a broad range of sound tests. This document is available at the link on the right side of this page. For specific project related questions or to schedule a Sound Control Lunch and Learn, please contact your Regional Representative at (800) 356-7887.