This paper is based on findings resulting from ASHRAE Research Project RP-1219.

Duct rumble noise in HVAC air distribution systems is commonly attributed to the poor aerodynamic discharge conditions of fan outlets. To date, qualitative descriptors published in ASHRAE Handbooks have been used as design guidelines for engineers to limit the amount of duct rumble noise. The objective of this study was to design, build, and verify a test facility that could be used to accurately quantify the amount of duct rumble noise that is caused by the change in discharge conditions of a fan and duct system. The measured changes in the noise level needed to be due to the change of the discharge configuration and not outside influences on the system. To cover a large range of typical installation configurations the test facility was to be capable of changing between fourteen different discharge conditions, consisting of four different fan orientations and different distances between the fan outlet and the primary duct inlet. Further, the fan was operated at eight operating points on the fan curve that were chosen to cover the full operating range of a fan. The design and evaluation of the test facility is described.

Units: I-P