Preliminary testing for ASHRAE research project 1919: The effects of duct size and aspect ratio on flow noise in elbows

The goal of RP-1919 is to investigate the regenerated noise and breakout noise of elbow fittings, eventually resulting in an algorithm for a variety of flow rates that considers a duct’s size and aspect ratio. This algorithm is intended for more accurate noise prediction of elbow fittings, to better inform building design. The practical application of this project necessitates a test method that is applicable to real-world building systems. Sound intensity measurements are a logical choice to investigate the elbow fittings, with one notable challenge: differentiating airflow noise from elbow fitting noise, especially at high flow rates that an intensity probe would not typically accommodate. Preliminary testing has been done to investigate the use of a blimp style windscreen and faux-fur muff with intensity scanning; this windscreen configuration can be seen used in film and TV production to get high quality audio where extreme conditions may affect sound. This presentation will discuss initial findings from the windscreen investigation.