Estimate HVAC duct noise from airflow, duct size, air velocity, distance, duct liner, bends, dampers, and grille noise. This calculator gives an approximate duct noise level, final room noise level, velocity category, and comfort rating.
Airflow and duct size:
The calculator estimates duct area and air velocity from CFM or m³/s.
Noise adjustments:
Higher air velocity, fittings, dampers, and grille hiss add noise, while duct liner or silencers reduce noise.
Final room level:
Distance loss from the register to the listener is subtracted to estimate final duct noise at the listener.
A duct noise calculator helps estimate whether an HVAC duct, register, return, branch duct, or supply run may create noticeable noise in a bedroom, office, studio, classroom, or living area.
This is a simplified estimate. Real duct noise depends on airflow, duct shape, grille selection, turbulence, fan sound, vibration, duct liner, elbows, dampers, leakage, and room acoustics.
This calculator uses a simplified duct noise estimate:
Estimate duct velocity from airflow and duct area, apply a velocity noise adjustment, add fittings and grille penalties, subtract duct liner attenuation, then subtract distance loss to the listener.
Noisy ducts are often caused by high air velocity, undersized ducts, restrictive grilles, sharp bends, dampers, turbulence, rattling metal, vibration, and air leaks.
Common fixes include lowering fan speed, increasing duct size, reducing restrictions, using quieter grilles, adding duct liner or silencers, sealing leaks, and isolating vibration.
Lower duct velocities are usually quieter. As a rough guide, under about 500 fpm is typically quieter than high-velocity duct runs, though real comfort depends on room type and grille design.