Standard: ASTM E90: Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements
Certification Required: Acoustical certification is currently not required by building codes, however the STC rating is required by the IBC and IRC codes for demising walls and floor-ceiling assemblies in multi-family dwellings. STC and/or OITC ratings may be necessary for product or assemblies in certain types of buildings to meet the requirements in the ANSI/ASHRAE/ICC/USGBC/IES Standard 189.1, LEED, ANSI/ASA S12.60 Guidelines for Schools, FGI Guidelines for Healthcare Facilities, and International Green Construction Code. There are also OITC rating requirements for building facade and facade elements in New York City and other large cities.
Scope: This test method covers the laboratory measurement of airborne sound transmission loss of interior and exterior building partitions and elements. The data obtained from this test is used to calculate sound transmission class (STC) and outdoor-indoor transmission class (OITC) ratings in accordance with ASTM E413 and ASTM E1332 respectively.
Applicable Products: Windows, doors, interior and exterior wall constructions, floor-ceiling systems, roof assemblies, curtain wall and storefront systems, skylights, office screens and many other types of products. The ASTM E1425 standard practice specifies standard test sizes for windows, doors, curtain walls and skylight systems. Wall assemblies must be a minimum of 8’ wide by 8’ high but may need to be larger depending on the expected STC rating. Floor-ceiling and roof assemblies would need to be 10’ wide by 12’ long in order to fill the entire test frame.
Test Procedure: Two adjacent reverberation rooms are arranged with an opening between them. The product or assembly is installed into a test frame or filler wall which is then placed in the opening between the test chambers. Care is taken that the only significant sound transmission path between rooms is by way of the test specimen or partition. An approximately diffuse sound field is then produced in the source room. Sound incident on the test specimen causes it to vibrate and create a sound field in the receiving room. The space- and time-averaged sound pressure levels in the two rooms are determined. In addition, with the test specimen in place, the sound absorption and the background sound levels in the receiving room are determined. The sound pressure levels in the two rooms, the sound absorption in the receiving room and the area of the specimen are used to calculate sound transmission loss at the standard 1/3 octave band frequencies.
End Result: The test report will include the sound transmission loss values from 80 to 5000 Hertz, the STC rating and the OITC rating. The ISO international rating (Rw) can also be calculated if requested in advance. Sound transmission loss measurements may be conducted at some lower frequencies if requested in advance.
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