Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Noise generated in Air Ducts

Estimate noise generated by air flow in ducts.

Sponsored Links

Air flow in ducts generates noise. The noise in the duct is determined by

  • air velocity
  • duct size (cross sectional area)

Generated noise can be calculated with the empirical equation

LN = 10 + 50 log (v) + 10 log (A)                                                       (1)


LN = sound power level in the duct (dB)

v = air velocity (m/s)

A = air duct cross sectional area (m2)

The equation modified for imperial units

LN = 10 + 50 log (vi / 197) + 10 log (Ai / 1550)                                                      (1b)


vi = air velocity (ft/min)

Ai = cross sectional area (in2)

Air ducts - noise generated by air flow

Circular air ducts - cross sectional area

Example - Generated Noise in Duct by Air Flow

The cross section area of a 200 mm duct can be calculated as

A = π ((0.2 m) / 2)2)

   = 0.0314  m2

The noise generated in the duct with an air flow velocity 10 m/s can be calculated as

 LN = 10 + 50 log (10 m/s) + 10 log (0.0314 m2)

    = 45 db

The noise generated in the same 200 mm circular duct as above with air flow velocity 20 m/s can be calculated as

 LN = 10 + 50 log (20 m/s) + 10 log (π ((0.2 m) / 2)2)

    = 60 db

Note! - due to the noise generated by fans - noise generated inside ducts by air flow can in general be neglected.

Sponsored Links

Related Topics

Related Documents

Sponsored Links

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

About the Engineering ToolBox!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.


This page can be cited as

  • Engineering ToolBox, (2008). Noise generated in Air Ducts. [online] Available at: [Accessed Day Mo. Year].

Modify access date.

. .


3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

3 30

Sponsored Links