Basic Documentation

Chapter 3–HVAC Sound Sources
Chapter 3 discusses sources of sound associated with HVAC systems. It includes the
following topics:
• Sources of sound in HVAC systems
• Fan sound components
• Fan sound power level calculation
• Damper airflow noise
• Elbow airflow noise
• Junction and takeoff airflow noise
• Air delivery device noise
Sources of Sound in HAVC Systems
Sound associated with HVAC systems and equipment is generated from multiple sources. All
operating equipment generates sound by the inherent vibration of its components. This
includes HVAC fan systems, pumps, and the primary mechanical equipment (boilers, chillers,
air compressors, etc.). All of these units contain mechanically rotating components that
generate operational sound. This sound travels both as sound waves through the air and by
transmission of vibrations through adjoining elements of the building structure including walls,
floors, pipes etc.
In addition to the sound generated by the mechanical components of rotating equipment, the
air movement produced by a fan generates aerodynamic sounds due to interaction with the
distribution system components including dampers, duct fittings, junctions, terminal units, air
diffusers and inlet grilles.
Rotational equipment sound is primarily attenuated by isolating the equipment from occupied
areas of a building, incorporating physical barriers to sound waves and utilizing vibration
isolation to prevent vibrations from being transmitted through the building structure.
(Information on attenuating equipment operational sound is given in a later section.
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