ASTM C919-19 pdf download.Standard Practice for Use of Sealants in Acoustical Applications.
3. Terminology
3.1 Definitions—For definitions of terms used in this rec- ommended practice, see Terminologies C717 and C634.
4. Significance and Use
4.1 Walls, ceilings, and floors in building construction, especially those that are of lightweight construction, and that are designed to reduce or limit sound transmission, can have undesirable sound transmission characteristics if care is not taken to seal joints, voids, and penetrations that typically occur. Unsealed joints, voids, and penetrations will substantially increase the sound transmission characteristics of these types of construction. By sealing them the transmission of sound can be substantially diminished by eliminating “flanking paths.”
5. Sound Transmission Requirements
5.1 The construction industry has adopted Sound Transmis- sion Class (STC) units, as defined in Terminology C634, to rate the sound transmission properties of walls, ceilings, and floors. The STC is determined in accordance with Classification E413. The test data are obtained in accordance with Test Methods E90 and E336.
5.2 Various building and other governmental adopted codes include requirements for sound transmission.
5.2.1 For example, the International Building Code (IBC), Section 1207, has requirements for the amount of sound that is allowed to be transmitted through the interior walls, partitions, and floor and ceiling assemblies between adjacent dwelling units and between them and public spaces of a building.
5.2.2 Additionally, the department of Housing and Urban Development (HUD) has the following standard for STC limitations for various housing units: HUD Minimum Property Standards for Housing, Section 4910.1.
6. Why Seal Openings
6.1 The sound transmission of a wall, ceiling, or floor, no matter how well built, can be substantially defeated by the presence of unsealed joints, voids, and penetrations. Fig. 1 illustrates examples of how sound travels through unsealed joints, voids, and penetrations in walls and how sealing them will minimize sound transmission.
6.2 The effect of unsealed joints, voids, and penetrations on the STC rating of partition walls is illustrated in Fig. 2. For the sample wall example, with an STC rating of 40 that has openings that total 9 cm 2 (1.4 in. 2 ) will have its STC reduced to 36 a 10 % difference. However, that small difference results in a change to the apparent loudness of sound transmission to that which is twice as loud.
7. Positioning of Sealants
7.1 Fig. 3 illustrates placement of liquid-applied sealants to improve the STC rating from a value of 29 to a value of 53. Note that two properly placed sealants are sufficient and sealing beyond that is unnecessary.
8. Application of Sealants
8.1 Fig. 4 illustrates typical liquid-applied sealant applica- tions. Additional sealant application information can be ob- tained from Guide C1193 and manufacturers literature for specific products and applications. 9. Types of Sealants
9.1 Precured Sealants—Precured sealants include a wide variety of gaskets and tapes, and foamed shapes that have constant dimensions. These materials are effective sound seals when the tolerances for joint, void, or penetration opening can be accurately predicted and installed within those tolerances. A varying opening width along its length, which exceeds those tolerances, will cause the gasket, tape or foamed shape to have difficulty in maintaining a proper seal at all points with the constant compression that is necessary to effect a seal. Pre- cured sealants in the form of pads have proved to be effective for sealing electric, telephone, television and other types of jack and back boxes.
9.2 Non-Sag Sealants—These liquid-applied sealants can conform to the wide range ofsizes encountered in joints, voids, and penetrations especially those that have tolerances exceed- ing those applicable for precured sealants. The following types are available:
9.2.1 Nondrying, Nonhardening, Nonskinning Sealants— These types of sealants have proven to be effective in reducing sound transmission. By remaining flexible as well as perma- nently adhesive, they can maintain an effective seal. These types of sealants, for acoustical applications, normally are nonbleeding and will not stain walls. The nonskinning mate- rials should be used only in concealed areas. If however, they are exposed to view they are not paintable and may stain adjacent paint and other surfaces or pick up dirt.ASTM C919 pdf download.