AS 2499-1981

This standard sets out the method for the measurement of the attenuation by ceilings of airborne sound between two rooms with a plenum space above. It provides a means of evaluation of the sound isolating performance of a ceiling system under laboratory conditions. The airborne sound attenuation is defined in terms of the level difference in a randomly incident sound field; such a field is intrinsic to the test procedure.NOTES1. This method utilizes a laboratory space arranged so that it simulates a pair of horizontally adjacent, typically small offices or rooms sharing a common suspended ceiling system, plenum space, and dividing wall. The dividing wall extends to the underside of the ceiling system, which may be continuous or discontinuous at its intersection with the dividing wall. Plenum dividers may be installed above the dividing wall.2. In the prescribed configuration, special design features ensure that the only significant sound transmission path is by way of the ceilings and the common plenum space. The facility is to be used for measuring the noise reduction, room-to-room, of the ceiling/plenum system.3. Within the construction limitations given in Clause 2.5, the quantity being measured by this method is the sound attenuation of a suspended ceiling installed in the prescribed laboratory environment.4. The sound pressure level difference obtained from the prescribed test facility and test method is useful for rating and comparing, under standardized conditions, the sound isolation performance of ceiling materials mounted in specified suspension systems.5. The basic procedures can be extended to the study of the additional sound isolation that may be achieved by ancillary systems. These could include the application of materials used either as plenum barriers or as backing for all or part of the ceiling.6. The facility may also be used to study the simulated held performance or an integrated system comprising plenum, ceiling (including any fittings and building services such as luminaires and air-conditioning registers), and dividing wall. The latter may incorporate a variety of components such as doors, transoms, glazed sections or bookcases.

Reconfirmed 1990Under Revision see DR 99408 CP