Parametric study of circular duct breakout transmission loss

Publication Type:
Conference Proceeding
Australian Acoustical Society Acoustics 2021 Wollongong: Making Waves, 2021, pp. 41-46
Issue Date:
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Breakout from ducts can be a major source of noise on industrial sites. The emitted noise is harmful at sufficient levels and must be reduced. Reducing noise levels using appropriate methods after the fact can be both costly and time consuming. This can be avoided by correctly predicting duct transmission loss before the duct is installed and choosing a suitable construction. In this paper the breakout from circular ducts will be presented as part of a parametric study. Parameters such as duct radius and wall thickness will be used to allow for a suitable choice of duct construction. In practical systems duct radii can be several metres in diameter and this is reflected by the range of the study. The breakout noise is calculated using a semi analytic finite element method. The first step in this method requires determination of the duct's modal properties which is calculated using a numerical eigenvalue analysis. The waves are then propagated along the duct using an analytic expression. A monopole sound source is used to excite the system, simulating the complex acoustic field within HVAC ducts with the transmission loss calculated from the difference between radially propagating sound power to axially propagating sound power.
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