The commotion of traffic outside a kitchen window interrupts a relaxing morning routine. The cacophony of a nearby construction site infiltrates a classroom while students take an exam. The bark of a neighbor’s dog cuts through a restful night’s sleep.
Unwelcome sounds can spoil the intended experience in an interior space. While the prospect of controlling noise can conjure up images of unsightly foam panels, solutions can actually be integrated directly into a building design. Windows and doors offer opportunities to make homes, classrooms, offices or most any built environment discernably quieter and more comfortable.
Discover the real importance of managing acoustics, the industry methods for analyzing noise, and the desirable characteristics of sound-insulating windows and doors.
Noise from outside can be a bother, but is it a priority to address when building or renovating? Surprisingly, sound affects people in observable ways. After only five minutes of exposure to regular traffic noise, individuals can exhibit physical and mental symptoms.
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Excessive sound can be stressful, and the body reacts accordingly. A person may experience an elevated heart rate and higher blood pressure, and they may begin to feel fatigued. Symptoms can become more dramatic in extended or extreme cases of noise exposure. Beyond the immediate symptoms, hearing can also be damaged. The World Health Organization (WHO) reported, “Nearly 50 percent of people aged 12 to 35—or 1.1 billion young people—are at risk of hearing loss due to prolonged and excessive exposure to loud sounds.”
Psychologically, sound can lead to nervousness, agitation and a lack of focus. If hearing has been damaged, the abilities to hear high frequency sounds and communicate effectively with others are compromised. This is notably detrimental to young children as they are beginning to learn and socialize.
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These physical and mental symptoms have further effects in different everyday environments. Students in schools may score lower on exams. Employees in office settings may not be as productive. Workers in health care settings may make more errors. Families at home may lose quality sleep.
By considering acoustic performance, professionals in the construction industry have the opportunity to provide clients with valuable knowledge that will make their special spaces not just more pleasant but also decidedly healthier.
To assess the potential risks of sound, it is important to understand how it is measured and how to utilize those measurements.
Sound is typically measured in decibels (dB), but decibels do not measure sound as people often understand it. Two sounds of an equal decibel measure may not be perceived at an equal volume. To measure “loudness” as perceived by the human ear, there are separate units called A-weighted decibels (dBA).
- 30 dBA is a whisper
- 60 dBA is a typical conversation
- 70 dBA is a group conversation
- 91 dBA is a passing motorcycle or subway
- 95 dBA is a food processor or hairdryer
- 106 dBA is a gas-powered leaf or snow blower
- 112 dBA is a rock concert or chainsaw
- 120 dBA is a jet airplane takeoff
The danger of these noises isn’t simply a matter of a high A-weighted decibel measurement—the time exposed to a given sound is also critical. For example, a sound measuring at 85 dBA can only be endured for 8 hours without hearing loss. For each 3 dBA increase, this safe exposure time is halved: 88 dBA noise can only be endured for 4 hours before hearing loss, 91 dBA noise can only be endured for 2 hours before hearing loss, and so on. The U.S. Environmental Protection Agency (EPA) and WHO recommend keeping environmental noises below 70 dBA over 24-hour periods to prevent hearing loss.
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These above examples are largely relevant to louder workplaces such as manufacturing environments and entertainment spaces. When considering the home, office, and similar areas, it is important to note that conversation, sleeping, working, and recreation become difficult over a sustained 45 dBA noise level.
Sound infiltrates the built environment through open windows and doors and through building materials. A few common sources of noise include road traffic; air traffic; nearby construction; local businesses; and pets and wildlife.
There are two key ratings that measure how well a window, door, or another building material insulates against noise.
The first of these is Sound Transmission Class (STC). STC measures the transfer of sound through interior walls of a built environment, though it has been applied to most any space-dividing element.
The higher the STC rating, the better it is at blocking sound. For example, normal speech can be understood through building products with an STC rating of 25. Loud speech is audible but not understood through products with an STC of 35. Loud speech is perceived as a murmur through products with an STC of 40. Quality residential windows and doors usually have STC ratings measuring in the 30s. In commercial contexts, some window and door systems have STC ratings into the 40s.
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The second of these ratings is Outdoor-Indoor Transmission Class (OITC), specifically measuring noise transfer from the exterior to the interior of a space through walls, windows, and doors.
As with STC, the higher the OITC rating, the greater the sound insulation. The OITC ratings of residential windows and doors range from the mid-20s to the mid-30s. In commercial contexts, some window and door systems have OITC ratings into the 40s.
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STC and OITC cannot be directly compared. For example, an STC rating of 35 is not the same as an OITC rating of 35. This is because each measurement is based off a different range of sound frequencies; STC’s range focuses on the expected range of indoor sound such as speech whereas OITC’s range is expanded to consider typical outdoor noises like road and air traffic.
Windows and doors contain several components, each having a quantifiable effect on its overall acoustic performance. The framing and glazing are perhaps the most important to consider.
Framing of greater mass is more effective against sound. Using a variety of materials and additional insulating barriers will also enhance acoustic performance.
For glazing, using an insulated glass unit (IGU) is critical. IGUs have two or more glass panes in a sealed unit. The panes may be of dissimilar thicknesses or types or may even feature different coatings or laminations to increase acoustic performance. The content of the airspace is also critical. For example, IGUs that use air perform better at lower frequencies, whereas IGUs filled with argon perform better at higher frequencies.
Beyond framing and glazing, accessories like sills, thresholds, weatherstripping, and sealants also affect acoustic performance. And of course, a high-performance window will only operate at its full potential when properly installed.
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Though codes and standards are often reserved for commercial spaces, the acoustic performance of any built environment is important. It will affect the quality of life. Analyzing the whole environment and preparing for potential disturbances through high-performance windows and doors will ensure that a space will be a pleasant and healthy one—no matter the time of day or season.