Several years ago, TC 2.6, Sound and Vibration, adopted a long-range goal of completely revising and updating the methodology for system noise calculations shown in the ASHRAE Handbook—Systems Volume, chapter 35 (ASHRAE 1980). Since then, procedural weaknesses have been identified, priorities established, and .research projects undertaken to develop new data and methods. The results of this work, along with a new, simplified, and more complete calculative format are planned for inclusion in the 1984 Systems revision.

Five research projects, either completed or in progress, address specific areas in the methodology that were considered technically weak in previous chapters. These research projects cover attenuation in ductwork, noise generation and attenuation in fittings, low-frequency radiation from ductwork, duct breakout, and sound power/sound pressure level relationship in rooms.

These projects include both new testing and research, as well as extensive surveys of existing literature and normalization of data.

A revised system-noise calculation worksheet is being developed that more accurately represents air-handling and air-distribution systems and their noise generating/attenuating characteristics. This worksheet will also serve as the basis for future research and revisions to the state of the art in system noise calculation methodology.