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Acoustic Ratings For Partitions and Providing compete construction specifications Floors documentation, systems By Jay Bethel CSI and David Stutzman, AIA, CSI, CCS, SCIP, LEED AP and performance Acoustic Control performance. descriptions, and risk and Transmission Class (STC) is quality advisory services. There are two basic approaches to a reliable single-number rating for acoustic design: Sound Control and partitions' air-borne sound CSI Award Winning Publication Control. Sound control, transmission loss without regard for Conspectus's Tech Tips received the provides favorable conditions for the the acoustic properties of the rooms national Communications Award from separated by the partition. STC is CSI. perception of desirable within a space. , excludes or derived by comparing the ASTM E90 ABSTRACT: reduces unwanted sounds and tested transmission loss over 16 Improving acoustic ratings for vibrations, especially sounds to a standard reference partitions and floors depends on transmitted between adjacent contour according to ASTM E413. increasing sound transmission losses spaces. STC ratings are used to compare to minimize unwanted air-borne and acoustic performance of partitions. structure-borne sounds between Sound control is accomplished by the Noise Isolation Class (NIC) is a adjacent spaces. Effective noise finishes and furnishings installed in control improves functionality of each space. A combination of sound single-number rating that measures building spaces. control devices are used to reflect, air-borne between two FILING: absorb, diffuse, or diffract sound to rooms taking into account the UniFormat™ improve the sound perception within partition, transmission paths, and the B1010 Floor Construction the space. acoustic properties of the source and C1010 Interior Partitions receiving rooms. NIC is usually a field MasterFormat™ Noise control is accomplished, 09 21 00 Plaster and Gypsum Board principally, by the partition, floor, and test to assess actual installed Assemblies ceiling construction separating conditions. Noise reduction is 09 50 00 Ceilings adjacent spaces. Noise control measured according to ASTM E336 09 60 00 Flooring assemblies increase the transmission and compared to the standard contour KEYWORDS: loss of air-borne and structure-borne according to ASTM E413 to derive the Sound transmission class, noise NIC rating. isolation class, noise reduction class, sound between spaces attempting to Noise Reduction Coefficient (NRC) impact isolation class, , make unwanted sound imperceptible absorption, sound control, noise in the receiving room. is a single number rating for a building control This article will concentrate on noise material to absorb air-borne vocal REFERENCES: control measures for acoustic privacy range sound (250- 2,000 Hz). The ASTM C423 - Standard Test Method between spaces. rating is determined by lab testing for Sound Absorption and Sound according to ASTM C423. Because Absorption Coefficients by the Sound Ratings NRC ratings are an average for vocal Reverberation Room Method frequencies, a material may have very ASTM E90 - Standard Test Method Humans hear sound at frequencies for Laboratory Measurement of poor sound absorption at low or high Airborne Sound Transmission Loss of ranging from 20 to 20,000 Hz. The frequencies, and at certain vocal Building Partitions and Elements acoustic ratings for selecting range frequencies. ASTM E413 - Classification for Rating materials and assemblies are Impact Insulation Class (IIC) is a Sound Insulation normally evaluated at 6 octaves (125, single number rating for structure- ASTM E492 - Standard Test Method 250, 500, 1,000, 2,000, and 4,000 borne impact sound transmission loss. for Laboratory Measurement of Hz) associated with speech. The Impact Sound Transmission Through Impact sound pressure is measured common laboratory tested ratings Floor-Ceiling Assemblies Using the according to ASTM E492 using a Tapping Machine include the following. standard tapping machine and ASTM E989 - Standard Classification For all these ratings, a greater compared to a standard contour for Determination of Impact Insulation number indicates superior acoustic Class (IIC) TECH TIPS

www.conspectusinc.com Vol12.10.01 ©2012 Conspectus Inc. Page 2 of 2 according to ASTM E989. The IIC Common Approach Conclusion ratings are roughly equivalent to STC ratings. Minimize flanking paths. Any Achieving improved STC and IIC Required Ratings penetration, air gap, or other way for ratings, while challenging, is not sound to travel over, under, or around impossible. Careful design will ensure The International Building Code (IBC) a is called a "flanking path." the best possible performance in rated regulates noise control for residential Flanking paths can include assemblies. occupancies, only Section 1207 ductworkpiping, other partitions, An acoustical design consultant may requires dwelling unit separation doors, windows, receptacles, fixtures, be the best investment to ensure code assemblies to have air-borne (STC) other penetrations and connecting compliance and satisfactory building and structure-borne (IIC) ratings of not construction. The initial effort to performance after occupancy. less than 50 if lab tested, and not less achieve greater acoustic performance Additional Resources that 45 if field tested. Other building is to control these weak points in the and use types require noise control assembly. www.stcratings.com - Offers designs to make the spaces useable. Here are strategies that may be useful descriptions of rating systems, links to The Gypsum Association GA-600 Fire for improving STC and IIC other rating systems, and suggestions Resistance Design Manual, available performance. on enhancing performance of wall as a free download, includes fire Improving Wall STC Ratings: systems. resistance, STC, and IIC ratings for  Extend to structural decks. www.nrcratings.com - similar website more than 230 wall and floor for NRC ratings. assemblies. Multiple IIC ratings are  Seal penetrations, openings, and reported for various finishes applied to perimeter to eliminate air paths each floor assembly. using acoustical sealants. Acoustical Design  Increase wall mass.  Use unbalanced faces (e.g. 2 layers Every building and interior space has of gypsum board on one side and 1 different acoustic requirements. The layer on the other). requirements for a Medical Intensive Care Unit would be quite different  Increase wall insulation for exterior from those of a kindergarten or a walls, and include insulation for concert venue. Because the various interior walls. sound ratings generally address only  Use resilient furring channels. speech frequencies, the ratings may be ineffective in evaluating materials  Use dual, staggered stud layouts. Add Your Comments and assemblies used to isolate  Select doors, windows, and other We invite your comments. Visit our blog sounds outside the speech opening with an STC rating and add your comments. range such as music and low matching the wall assembly. frequency mechanical equipment. Like it? Share it!  Increase air space within the wall. The sound transmission between Tweet or Email your friends spaces is dependent on the acoustical  Use metal instead of wood studs. properties of source and receiving  Improving Floor IIC Ratings: The information contained in this document space including each material within is offered for educational purposes, only, the spaces, the size of the spaces,  Install a soft, resilient surface. and not as technical advice suitable for any and construction of the enclosing  Use a floating floor system with a particular project or specific condition. assemblies. A comprehensive design resilient cushion. Technical consulting is unique to the facts that addresses particular sound of a particular condition, and Conspectus transmission requirements is a  Install a solid suspended ceiling recommends that a specialist be consulted complicated affair, most effectively below the floor. to determine solutions for each specific completed by an acoustical  Include insulation within the ceiling condition. consultant. cavity.