Duct Breakout Noise
Duct Breakout noise describes noise transmitting through the walls of sheet metal duct. Where ductborne noise travels along a ducted path to air terminals, duct breakout noise transmits directly through duct walls and into receiving spaces in close proximity to noise producing equipment.
Calculate Break-Out Noise with a Branch
Because these are usually applied at a specific point along a duct system, a branch can be used to take advantage of existing calculation paths.
To begin a duct breakout noise calculation, drag the Duct Breakout element onto the canvas. A drop zone appears just below your cursor, which will drop the element into the existing calculation path. For duct breakout noise calculations, use the “Branch” drop zone. Placing the element here will create a branch, which captures all upstream elements of the calculation, along with the new Duct Breakout element, in a new calculation path.
Branch “drop zone” to calculate duct breakout noise using the branch feature.
There are normally 3 elements used to predict duct breakout noise:
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Duct Breakout. Calculates the difference in sound power level inside the duct, to outside the duct. This considers duct size, duct length, internal duct liner, and mass of duct.
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Ceiling System. Library reference to Ceiling data, which can be modeled as Transmission Loss, Ceiling Attenuation Class, or Ceiling+Plenum+Room Attenuation, depending on how you prefer to conduct your calculations.
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Room Effect. Classic Diffuse: Line Source element is often used to model the radiation of noise from a duct expressing over an occupied space.
Three (3) elements typically encompass duct breakout noise calculations.
Calculate Break-Out Noise using “In-Line” Method
The “In-Line” method is intended streamline basic duct breakout noise calculations. For this method, select the point along the duct system where you’d like to check duct breakout noise levels. Then, click the Duct Breakout In Line calculation module. The In Line method aggregates the Duct Breakout, Ceiling and Line Source Room Effects into a single element to simplify the calculation.
“In-line” duct breakout noise calculation element.
Results are displayed “in-line” with your existing calculation path, without affecting the results of the path, providing a more intuitive user interface when your checking duct breakout noise at multiple points along the duct system.
“In-line” duct breakout noise calculation results.
With these 2 methods, you’ll have the flexibility to model any duct breakout noise scenarios you might encounter in your project.