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

This paper discusses measurements of the acoustical and airflow performance of interior natural-ventilation openings and silencers (‘ventilators’) in existing buildings. It reviews the characterization of ventilator performance, and methods and theory for measuring it. Performance measures for sixteen ventilators in five buildings are presented and discussed. The measured acoustical and airflow performance of rectangular ventilation openings in thin partitions is slightly better than the theoretical performance of a sharp-edged, rectangular opening. The measured performance of slot openings next to reflective surfaces is similar to the theoretical performance of a sharp-edged, rectangular opening. Adding absorptive material to a surface next to a slot opening increases the sound-transmission loss by about ASTC 5, with negligible reduction in airflow. Duct-like ventilation openings have airflow performance approximately 50% greater than for a thin opening of the same cross-section. Z-shaped crosstalk silencers were measured to reduce sound transmission by at least ASTC 16, and only slightly to restrict airflow. Adding a grille to a ventilation opening results in negligible change in sound transmission, but approximately halves airflow.