Noise Generated in Air Ducts

Calculate the sound power level generated by air flow in ducts based on air velocity and duct cross-sectional area using empirical equations.

Calculator

Inputs

Results

Sound Power Level (LN)-- dB
ParameterMetric ValueImperial ValueUnit
Air Velocity (Example 1)103280.84m/s / ft/min
Duct Area (Example 1)0.031448.63m² / in²
Sound Power Level (Example 1)4545dB
Air Velocity (Example 2)206561.68m/s / ft/min
Duct Area (Example 2)0.031448.63m² / in²
Sound Power Level (Example 2)6060dB

Calculation Formula

Metric Units:

LN = 10 + 50 log(v) + 10 log(A)

Where:

  • LN = Sound power level in the duct (dB)
  • v = Air velocity (m/s)
  • A = Air duct cross-sectional area (m²)

Imperial Units:

LN = 10 + 50 log(vi / 197) + 10 log(Ai / 1550)

Where:

  • vi = Air velocity (ft/min)
  • Ai = Cross-sectional area (in²)

Notes

  • Due to noise generated by fans, noise generated inside ducts by air flow can generally be neglected in practice.
  • The calculation uses empirical equations based on experimental data.
  • For circular ducts, cross-sectional area A = π × (d/2)², where d is the diameter.