Noise Attenuation by Changing Duct Area

Sound attenuation when changing duct areas or dimensions:

dL = 10 log( ( 1 + A₁ / A₂ )² / 4 (A₁ / A₂) )                                                                (1)

where

dL = noise attenuation (dB)

A₁ = inlet area (m²)

A₂ = outlet area (m²)

Note! - valid only for sharp changes.

Example - Attenuation when changing the size of a duct

The attenuation of noise when the ratio between area before and after A₁ / A₂ = 5 - can be calculated as

dL = 10 log( ( 1 + 5 )² / 4 (5))

    = 2.5 dB

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

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!

Privacy

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.

Advertise in the ToolBox

If you want to promote your products or services in the Engineering ToolBox - please use Google Adwords. You can target the Engineering ToolBox by using AdWords Managed Placements.

Citation

This page can be cited as

• Engineering ToolBox, (2008). Noise Attenuation by Changing Duct Area. [online] Available at: https://www.engineeringtoolbox.com/duct-area-change-noise-attenuation-d_1408.html [Accessed Day Mo. Year].

Modify access date.

close

• Home
  • Acoustics
  • Air Psychrometrics
  • Basics
  • Combustion
  • Drawing Tools
    • 2D Schematic Drawings
  • Dynamics
  • Economics
  • Electrical
  • Environment
  • Fluid Mechanics
  • Gases and Compressed Air
  • HVAC Systems
    • Air Conditioning
    • Heating
    • Noise and Attenuation
    • Ventilation
  • Hydraulics and Pneumatics
  • Insulation
  • Material Properties
    • Boiling point
    • Density
    • Melting points - freezing points
    • Viscosity
  • Mathematics
  • Mechanics
    • Fasteners
    • Threads
  • Miscellaneous
  • Physiology
  • Piping Systems
    • Codes and Standards
    • Corrosion
    • Design Strategies
    • Dimensions
    • Fluid Flow and Pressure Loss
    • Heat Loss and Insulation
    • Pressure Ratings
    • Temperature Expansion
    • Valve Standards
  • Process Control
    • Control Valves
    • Documentation
    • Measurements & Instrumentation
      • Flow Measurement
      • Temperature Measurement
    • Risk, Reliability and Safety
  • Pumps
  • Sanitary Drainage Systems
  • Standard Organizations
  • Statics
    • Beams and Columns
  • Steam and Condensate
    • Control Valves and Equipment
    • Flash Steam
    • Pipe Sizing
    • Steam - Heat Loss and Insulation
    • Steam Thermodynamics
  • Thermodynamics
  • Water Systems