1.1 The sound isolation between two spaces in a building is influenced most strongly by a combination of the direct transmission through the nominally separating building element (as normally measured in a laboratory) and any transmission along a number of indirect paths, usually referred to as flanking paths. Fig. 1 illustrates the direct paths and some possible structural flanking paths. Additional non-structural flanking paths may include transmission through common air ducts between rooms, or doors to the corridor from adjacent rooms. Sound isolation is also influenced by the size of the separating partition between spaces and absorption in the receiving space, and in the case of small spaces by modal behavior of the space and close proximity to surfaces.

1.2 The main part of this test method defines procedures and metrics to assess the sound isolation between two rooms or portions thereof in a building separated by a common partition or the apparent sound insulation of the separating partition, including both direct and flanking transmission paths in all cases. Appropriate measures and their single number ratings are the noise reduction (NR) and noise isolation class (NIC) which indicate the isolation with the receiving room furnished as it is during the test, the normalized noise reduction (NNR) and normalized noise isolation class (NNIC) which indicate the expected isolation when the receiving room is a normally furnished living or office space that is at least 25 m³ (especially useful when the test must be done with the receiving room unfurnished), and the apparent transmission loss (ATL) and apparent sound transmission class (ASTC) which indicate the apparent sound insulating properties of a separating partition. The measurement of ATL is limited to spaces of at least 25 m³ where modal effects create fewer problems. With the exception of the ATL and ASTC under specified conditions, these procedures in the main part of the test method are only applicable when both room volumes are less than 150 m³.

1.3 The NR and NIC between two locations may always be measured and reported though conditions present will influence how measurements are made. Restrictions such as minimum room volume or dimensions or maximum room absorption are imposed for all other measures and ratings in this standard. Thus, conditions may exist that will not allow NNR (NNIC), ATL (ASTC) or FTL (FSTC) to be reported. Where a partition between rooms is composed of parts that are constructed differently, or contains an element such as a door, it is not possible to measure the ATL and ASTC of the individual elements or portions of the partition. To evaluate the field performance of a door less than 6 m² in area, use Test Method E2964. The various metrics are inherently different quantities, so that NIC cannot be used instead of NNIC or ASTC when specifications are written in terms of one of those metrics that cannot be reported with the conditions present.

1.4 Annex A1 provides methods to assess the sound transmission through a partition or partition element with the influence of flanking transmission reduced. These methods may be used when it must be demonstrated that a partition has achieved a specified minimum sound attenuation. The results are the field transmission loss (FTL) and field sound transmission class (FSTC).

1.5 Annex A2 provides methods to measure the sound isolation between portions of two rooms in a building separated by a common partition including both direct and flanking paths when at least one of the rooms has a volume of 150 m³ or more. The results are the noise reduction (NR) and noise isolation class (NIC).

1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.7 The text of this test method references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.

1.8 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.