What factor may cause noise due to air velocity in an HVAC system?

In an HVAC system, noise caused by air velocity is significantly influenced by static pressure. Static pressure is the resistance to airflow within the duct system, and it can directly affect how fast air moves through the ducts. When static pressure is high, the air has to work harder to pass through, which can create turbulence and noise. Conversely, if the static pressure is too low, it can lead to insufficient airflow and potentially increased noise as well, as the system struggles to move air effectively.

In contrast, while duct size and flow rate are important for overall system efficiency and performance, they are more about the dimensions and volume of air being moved rather than the specific noise characteristics caused by air velocity. The feed temperature, while it plays a role in system performance and comfort, does not directly relate to the noise caused by air movement through the ducts. Therefore, static pressure emerges as the key factor in causing noise due to air velocity in an HVAC system.