Case study of HVAC noise in a conference room under varying operating conditions

Conference rooms are acoustically sensitive environments due to the need for high speech intelligibility both in-person and over teleconferencing systems. Room noise from building systems is a key contributing factor to speech intelligibility. Mechanical design, and in turn noise control design, focuses on peak heating and cooling demand; however, operating conditions vary based on the demand at any given time. This case study presents sound pressure level measurements from a conference room on the top floor of an office building, which was below a mechanical penthouse. The measurements were guided by ANSI/ASA S12.2, "Criteria for Evaluating Room Noise." Commissioning and developer agents varied the operating conditions of the entire building heating and cooling system to identify the primary contributors to room noise levels in the conference room, which varied as much as 13 dBA over background. Particular attention is given to the correlation between room noise levels and airflow from the air terminal unit serving the space. Comparisons between measured noise levels and noise modeling predictions are also provided.