For years, ASHRAE has maintained a position of prominence in developing standards and guidelines for the acoustical design of HVAC systems. Because of this leadership, the ASHRAE Handbook essentially has become a de facto standard and reference source for addressing a broad range of mechanical noise control applications.

The 1984 handbook will contain revisions in the procedures previously recommended for analysis and assessment of potential acoustical problems. These revisions, which result from recent research sponsored by ASHRAE, are likely to be controversial because of potential impact on present industry practices in publication of application guidelines for the selection of sound-rated products.

This paper discusses revisions in the equation for conversion from sound power to sound pressure level and how this may affect present product selection procedures using published sound rating data. The question of ceiling sound transmission loss is also discussed as it relates to application of "radiated" noise data for devices installed above an occupied space.