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# Lined Sheet-Metal Ducts - Sound Attenuation

## Noise attenuation in rectangular straight, lined, sheet metal ducts.

Attenuation in ducts with 25 mm lining are indicated below:

Attenuation in ducts with 50 mm lining are indicated below:

### Example - Sound Attenuation in Lined Duct

The sound attenuation in 610 x 610 mm lined duct is approximately 2.5 dB/m at frequency 250 Hz. The sound attenuation in 10 m duct can be calculated as

(10 m) (2.5 dB/m) = 25 dB

## Related Topics

• ### Acoustics

Room acoustics and acoustic properties. decibel A, B and C calculations. Noise Rating (NR) curves. Sound transmission through walls. Calculate sound pressure, sound intensity and sound attenuation.
• ### Noise and Attenuation

Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.

## Related Documents

• ### Sound - Attenuation and Speed vs. Sound Frequency and Air Humidity

The speed and attenuation of sound in moist air varies with sound frequency and air humidity.
• ### Sound Attenuation - Duct split to Terminals

Estimating sound attenuation where ducts splits to terminals.
• ### Sound Attenuation - Main Duct to Branch Ducts

Sound attenuation from main ducts to branch ducts.
• ### Sound Attenuation in Duct Elbows

Noise attenuation in duct elbows by reflected sound.
• ### Sound Transmission through Duct Walls

Sound transmission from ducts to surrounding rooms.
• ### Unlined Sheet-Metal Ducts - Sound Attenuation

Noise attenuation in unlined sheet-metal ducts.

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## Citation

• The Engineering ToolBox (2003). Lined Sheet-Metal Ducts - Sound Attenuation. [online] Available at: https://www.engineeringtoolbox.com/sound-attenuation-ducts-d_75.html [Accessed Day Month Year].

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