Page 52 - 2016Fall

Residential Quietude
findings at the 169th Meeting of the Acoustical Society of America in Pittsburgh, PA (Schnitta, 2015). It was re- warding afterward when people who either they or their spouse had a thyroid problem approached me to express gratitude for the brief explanation of the phenomenon.
• The control of noise and vibration for industrial appli- cations has been extensively researched for hearing loss prevention. The extensive work in this area was recently well summarized by William J. Murphy (2016).
The same level of insight, research, and understanding about quietude is slowly beginning to be applied to residential ap- plications and becoming part of standards and laws. It has become more common for architects to consider quietude in their work, resulting in more studies and resources to pro- vide the best products for their clients. Over the many years of observing construction, I have seen residential contrac- tors go from viewing the acoustic treatment as a nuisance unnecessarily delaying their schedule to embracing us to provide a product that makes their client very happy.
It is the goal of this article to provide a factual foundation for “quietude” to facilitate the communication of the concept to the homeowner, contractor, architect, project manager, and owner's representative. A clear explanation, with examples, on why residential acoustics and vibration control should be nonnegotiable considerations in any residential building is included so that all parties involved with a project will re- alize both the importance and the possibilities of quietude within any budget.
As scientists, we are trained to mathematically model the signal and the noise. That mathematical foundation with supportive research in the field has led to understanding what creates a better wall or floor, whether by a product or method of installation. It is this understanding that pre- vents common problems that exist between the design and the installation stages of any construction that often result in costly mistakes or render the acoustical treatment inef- fective. Even a rudimentary introduction to how sound and vibration interact with an environment will allow architects, designers, and contractors to effectively adapt to any chang- es or conditions that may occur in the field.
Basic Acoustic Criteria for
Residential Construction
Sound transmission class (STC) and impact insulation class (IIC) are the two relevant measures used to quantify sound separation across a partition such as a wall or floor. STC is a
measurement of an assembly’s ability to attenuate or reduce airborne sound transmission. IIC is a measurement of an as- sembly’s ability to attenuate or reduce impact sounds such as footfall noise.
STC
One common problem for homeowners and contractors when choosing the optimum product to achieve quietude is that users and clients often don’t have the ability to translate frequently used acoustical terms and standards for practi- cal applications. One example is STC. Specifically, STC is a single-number rating calculated in accordance with the American Society for Testing and Materials (ASTM) classi- fication E413 for sound transmission loss by a partition such as a wall or ceiling. If the goal is to build a wall that prevents sound from entering one room from another, knowledge of the STC rating of materials used as well as how that wall is to be constructed is paramount. This is similarly true for floors, walls, windows, and doors. Whatever materials are utilized, it is equally important that they be properly installed to have a rating that meets at least the minimum requirements of a client.
Generally, the STC of an acoustic barrier can be interpreted with the following levels on the far side of the barrier from the source:
25 - Normal speech can be understood quite clearly 30 - Loud speech can be understood fairly well
35 - Loud speech is audible but not intelligible
45 - Loud speech is very faint
48 - Some loud speech is barely audible
50 - Normal speech is not audible, but amplified sound will be audible
60 - Minimum requirement to inhibit audibility of sound that is amplified
Examples of Some Standard Wall Construction and Associated STC
Books have been written about various wall configurations (Beranek, 1991; Harris, 1998). At this time, giving an acous- tic value to standard walls, as shown in Figure 1, will facili- tate the conversation of laboratory versus field results, some- thing that is often overlooked or not understood.
Laboratory Versus Field Results
Most city building codes require the STC of the wall and floor to be 50. There are, however, two common problems with that simple requirement. The first is that a high STC
50 | Acoustics Today | Fall 2016