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Sound Control For Commercial And Residential Buildings Table Of Contents How Noise Effects Us Methods Of Sound Control 1 nwanted sound – or Sound Transmission Class (STC) And Sound Control 1 noise – that travels The Effects Of Insulation Thickness from room to room, And Density On STC Ratings 2 U from home to home, or office to Controlling Impact Noise 2 office, may have a direct impact Improving Office To Office Sound Reduction 2 on people’s notions of privacy, Controlling Exterior Sounds 3 as well as their work efficiency. Examples Of Ways To Construct Walls And The noise produced by appli- Floors/Ceilings To Achieve Desired STCs 4 ances, piping, heating and air- Sound Isolation Design Criteria 5 conditioning systems, phones, Guide Specification for Fiber Glass Acoustical Insulation 7 radios,TVs and talking are Typical Wall Assemblies among the major reasons people Single Wood Stud Walls 8 Staggered Wood Stud Walls 9 are dissatisfied with the privacy Double Wood Stud Walls 10 Metal Stud Walls 11 found in homes or office build- Exterior Walls 12 ings.Additionally,external noises Typical Floor/Ceiling Assemblies 14 such as traffic, sirens and Recommended Construction Methods for Controlling Sound 15 extreme weather conditions are Glossary 20 equally disturbing. Designing Bibliography 21 structures to control noise effec- tively can make homes and offices much more pleasant places in which to live or work. This Sound Control Guide recommends ways to Decibels And construct walls and other assemblies using fiber glass Sound Transmission Class insulation to help provide quality noise control. The decibel (dB) is used to express sound intensity The North American Insulation Manufacturers or loudness.The more intense a sound, the higher the Association (NAIMA) developed these recommenda- dB level.The sound transmission class (STC) is a tions based on the results of numerous acoustical tests numerical rating of the ability of a wall, floor/ceiling using American Society for Testing and Materials assembly or any other building element such as a (ASTM) methods. However, the recommendations are door or window to minimize sound transmission. presented here solely as a guide. NAIMA cannot guar- The higher the STC rating the more the sound is antee, does not represent or warrant, and assumes no blocked or reduced by the building element (See Table responsibility for building design or construction 1). For party walls or walls separating dwelling units, results based on information provided in this booklet an STC of 50 is considered barely adequate for because many other factors – including overall design providing privacy.STCs above 55 are required to and workmanship – are outside its control. provide acceptable privacy. Methods Of Sound Control TABLE 1 – STC Ratings Noise is unwanted sound that is transmitted by vibra- Sound Noise tion through air,walls, floors or ceilings. In a home or Transmission Speech Control Class (STC) Audibility* Rating office,there are three ways to control sound transmission: 15 to 25 Normal speech easily Poor understood. I Increase the mass of partitions 25 to 35 Loud speech easily Marginal I understood. Normal Break the path of vibration speech 50% understood. I Cavity absorption. 35 to 45 Loud speech 50% Good understood. Normal speech faintly heard, but not understood. Increasing the mass of walls and other structures can 45 to 55 Loud speech faintly heard, Very Good present a problem in lightweight construction because but not understood. the increased weight may not be structurally practical or Normal speech usually inaudible. aesthetically pleasing, not to mention more expensive. 55 and up Loud speech usually inaudible Excellent Breaking the vibration path – commonly called *Given a typical background noise level discontinuous construction – offers a practical method of of 30 dB on the “listening”side reducing sound transmission by as much as 6 to 10 dB. Cavity absorption, which uses fiber glass insulation to fill the space in walls and floors/ceilings, can further improve performance of discontinuous constructions acoustical analysis should be obtained from an acoustical by 5 to 15 dB. engineer when isolating sound from locations such as music practice rooms,recording studios,large conference rooms and mechanical equipment rooms. Sound Transmission Class (STC) And Sound Control Ratings Based On Lab Tests STC ratings are a measure of the effectiveness of a given STC ratings are based on laboratory tests conducted partition construction in reducing airborne sound trans- under ideal construction conditions. Partition manufac- mission.Because of the frequency range covered (125- turers acknowledge that the field STC of a partition can 4000 Hz),STC ratings are best used to evaluate speech be up to 15 - 20 points lower than laboratory values privacy for partitions and floors/ceilings separating adja- depending on the quality of detailing and workmanship. cent offices,rooms in one and two family dwellings,hospi- Therefore, the importance of communication between tal patient rooms,classrooms,dormitories,apartments, the design team and the construction team cannot be courtrooms,small conference rooms,etc.A more extensive overemphasized. 1 Fiber Glass Insulation The Effects Of Insulation Thickness Reduces Sound Transmission And Density On STC Ratings Fiber glass insulation in a partition or floor/ceiling Insulation thickness has a more significant effect on assembly significantly reduces sound transmission. STC ratings than does density.For a typical steel stud wall It also reduces sound transmission in roof/ceiling construction,the first inch of fiber glass insulation can assemblies. It is economical, lightweight and easy to increase the STC value 6 or more points.Each additional install. Some fiber glass insulation manufacturers sell inch of fiber glass insulation increases the STC value from acoustical or sound control batts for use in partitions. one to two points.Conversely,density variations have These batts are designed for easier installation in minimal effect on the STC rating.(See Table 2.) metal and wood stud partitions.They are essentially the same as their corresponding thermal batts, except that they may differ slightly in size and density.A Controlling Impact Noise partition with either fiber glass sound control or ther- Walls are rated only in terms of their STC value. mal batts having similar properties would achieve the Floor/ceiling assemblies – because they must also same STC rating. control sounds caused by impacts (such as walking or moving furniture) – are rated in terms of their STC and their impact insulation class, or IIC. Factors That Degrade Performance A person walking on a floor creates impact noise The presence of flanking paths,interconnecting that is readily transmitted to the room below.While ductwork,non-airtight edge joints,inadequate door carpets and pads can cushion impacts and reduce the and window constructions,untreated pipe and generation of impact noise, fiber glass insulation can conduit penetrations,etc.,all degrade the expected reduce impact and airborne noise transmitted through performance of a sound rated assembly.When proper the floor/ceiling assembly.As with STCs, the higher the attention to construction details are followed,field IIC value of a floor/ceiling, the better its ability to STC values can be equal to or even greater than labo- control impact sound transmission.An acceptable IIC ratory values. rating is typically 50 or above. Differences Between Lab Tests Not Unusual Improving Office To Office Partitions with STC ratings within 1-2 points Sound Reduction (1-2 dB) of the listed criteria would still be accept- In offices where the separating partition stops at the able given the anticipated tolerances in repeat ceiling, sound can flank around the partition by travel- tests. In fact, differences between testing labs of 2- ing through the ceiling.This flanking sound travels up 5 dB on identical test configurations are not through the ceiling in one office, across the top of the unusual. (Subjectively,the human ear would partition and then down through the ceiling in the consider a 1-2 dB change as “nondiscernible” adjacent office. In many offices this flanking path is at best, which is insignificant.) significant and degrades the sound isolation between offices.This is particularly true if the STC of the sepa- STC Requirements Are From AIA rating partition is greater than 45. The STC requirements in Table 3 (pages 5-6) are from the American Institute of Architects (AIA) and assume TABLE 2 – STC Values of Equal Thicknesses of acceptable background noise levels on both sides of Fiber Glass Insulation 5 1 the construction assembly.Normal background noise 3 ⁄8" steel studs; single layer ⁄2" gypsum board each side on the listening side of a partition has the effect of Material Thickness Density STC masking transmitted sound that might otherwise be Fiber Glass 2" 0.75 pcf 46 objectionable.In fact,sound transmitted through a Fiber Glass 2" 1.30 pcf 46 partition will be inaudible if its sound level is below Fiber Glass 2" 3.00 pcf 46 the level of the background noise. 2 Fiber Glass vs. Cellulose Insulation the type of grid system.The CAC is the single Manufacturers of cellulose insulation claim that number rating used to express the sound reduction their insulation, when used in a partition, gives or attenuation between two rooms sharing a higher STC values than fiber glass insulation.This common ceiling and/or plenum (See ASTM standard is not true. E 1414).These CAC improvements can be achieved 1 Numerous sound transmission loss tests by using unfaced 3 ⁄2 to 4 inch thick batts (R-11 conducted at independent laboratories have shown batts).The batts only have to be placed on the back that there is no significant difference in STC ratings of the ceiling panels on both of sides of the parti- using either fiber glass or cellulose insulation.The tion a distance of 4 feet back from the partition.

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