Laboratory measurement of the acoustical and airflow performance of interior natural-ventilation openings and silencers

Abstract

This paper discusses laboratory measurements of the acoustical and airflow performance of interior natural-ventilation openings and silencers (‘ventilators’). The objective was to create and characterize a purpose-built test facility, and use it to measure the combined acoustical and airflow performance of a number of ventilators of interest, to understand and optimize it, and provide design guidelines to practitioners. The paper discusses the characterization of ventilator performance, and methods and theory for measuring it. The design and performance of a purpose-built, two-room laboratory facility are described. The facility was used to investigate the performance of a non-acoustical grille, an acoustical louver, slot ventilators, crosstalk silencers and a novel door-vent silencer. The results identify a number of best practices for successful ventilator design: non-acoustical grilles should be avoided; the addition of a glass-fiber absorptive liner to the surface adjacent to a slot ventilator increases acoustical performance by STC 3–6; acoustically-lined crosstalk silencers can be very effective – the straight configuration is best and performance increases with the length of the flow path; acoustical liners should be at least 50-mm thick. A prototype door-vent silencer showed very promising performance, but needs to be optimized.