Noise Management
Ambient Noise
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North Americans spend 90% of their time indoors so it can be safely argued that the indoor environmental quality (IEQ) of a building has a significant impact on the health and productivity of its occupants. Occupant comfort, both thermal and acoustical, is essential components of IEQ. Expanded Polystyrene (EPS) insulation helps maintain a consistent air temperature; providing thermal comfort and reduction in noise transmission through both interior and exterior walls. EPS is manufactured with pentane, a hydrocarbon blowing agent that is not harmful to the stratospheric ozone layer and which diffuses during or shortly after the molding process is complete. Since the blowing agent is rapidly replaced by air, the installed insulation does not experience off-gassing that may affect indoor air quality (IAQ). |
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Expanded polystyrene does not contain harmful formaldehydes. The American Lung Association’s (ALA) Health House guidelines, among the toughest in the nation for indoor air quality, acknowledges EPS sheathing as a safe material to insulate foundation walls and floors. Although ALA representatives do not promote specific materials or products, they cite that expanded polystyrene walls release no lung damaging fibers.
Noise Reduction
One of the major performance benefits of Ultra Frame Insulated Panels is their superior sound reduction. With recent awareness of the adverse effect of excess noise on personal health, comfort, work efficiency and privacy, Ultra Frame applications are especially beneficial in diminishing noise transmission in structures such as hotels, condos or multi-family buildings, theatres and structures near airports and busy roads.
The sound audibility of speech ranges from 25–50 decibels (DB). At 35 decibels the human ear can hear speech that is loud but unintelligible. A typical 3-1/2” Ultra Frame wall with 1/2” Gypsum board on both sides can reduce sound transmission in a room to 30 DB. When component materials such as resilient channel and Gypsum board are factored in, sound abatement properties can increase up to 70 DB depending on the thickness of the application.
Essential to complying with the health, safety and welfare provisions of building codes is the ability of assemblies that separate spaces or occupancies within a building to reduce or restrict the transmission of sound. This is specifically identified for residential occupancies where code provisions cite minimum values for building construction to achieve, in this case the values are specified as Sound Transmission Class (STC) for walls and floor/ceiling assemblies and Impact Insulation Class (IIC) for floor/ceiling assemblies only. Other occupancies (Such as offices, education, assembly, etc.) are not normally specifically identified in the codes, but building owners may require self mandated specifications regarding STC and IIC ratings.”
In order for sound to be transmitted it requires an elastic medium where particles vibrate. The most common medium is air, but sound is also transmitted through building materials. When airborne sound is generated air particles vibrate, and when they encounter stiff building elements they induce oscillations in these materials that in turn induce oscillations in the air in neighboring rooms. Impact sound occurs when an impact to a building element induces oscillations within that element that are transferred to the neighboring air and through to other building elements.
Similar to other construction assemblies, the sound ratings of steel-framed assemblies are specified in STC rating (for walls) (see Table 1 for STC ratings for typical construction materials) or IIC rating (for floors). A wall assembly of a Sound Transmission Class (STC) of 45, for example, indicates the rating of the insulation (or isolation) of airborne sound provided by a barrier (such as the gypsum board). A floor assembly of an Impact Insulation Class (IIC) of 50 indicates the floor assembly’s effectiveness in retarding the transmission of impact sound. The higher the assembly rating (STC or IIC) the more sound proof the assembly.
There are several types of sound transmission, and the two types that are related to building construction are discussed below:
Airborne Sound Transmission: Airborne sound can be measured by generating a steady sound of a particular frequency in one room (source room) and comparing it with sound pressure level in an adjacent room (receiving room). The level difference is simply the difference between the source and the receiving levels. However, the level difference is influenced by the acoustic absorption in the receiving room. This is measured by the reverberation time (the time taken for a reverberant noise to decay by 60 dB).
Impact Sound Transmission: Tends to be most relevant for floors. It arises from a variety of sources, most notably the movement of people within a building, but also from such things as the slamming of doors. A standard impact sound source (tapping machine) is used to strike the floor and the impact sound pressure level is measured in the room below. Measurements in a building can be standardized to a reverberation time of 0.5 seconds, giving the Standardized Impact Sound Pressure level.
STC and IIC Requirements From Selected Codes
1Use Group R includes all structures in which families or households live, or in which sleeping accommodations provided, excluding those classified as institutional occupancies.
2Dwelling units are defined as dwelling units in two-family dwellings, townhouses & apartments buildings, guestrooms & guest suites in hotels and dormitories, sleeping rooms in lodging & rooming houses, and residential board and care occupancies.
