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Advances in Acoustics and Vibration
Volume 2015 (2015), Article ID 361678, 8 pages
http://dx.doi.org/10.1155/2015/361678
Research Article

An Image Based Mathematical Model for the Propagation of Fan Noise in a Plenum with Large Side Openings

Gannon University, 109 University Square, Erie, PA 16541, USA

Received 6 April 2015; Accepted 15 September 2015

Academic Editor: Gurvinder S. Virk

Copyright © 2015 Michael J. Panza. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper presents another application of an images group model for a special enclosure geometry and source orientation. A previous work outlined the concept via application to a special tight-fitting enclosure. Application of the concept to a fan plenum requires different mathematical descriptions for the image groups. This paper describes the sound reverberation inside a sound enclosure with mostly open sides where the primary noise sources are the air inlets and exhausts of axial type fans located at the top of the enclosure, the sound transmission through the air inlet openings, and the radiation to wayside positions. The main reverberation between the floor and ceiling is determined with an image based mathematical model. The model considers how the main reverberant part image group is amplified by its images from two parallel bulkheads and any side wall frame members. The method of images approach allows the hard surfaces of an untreated plenum to be represented by perfectly reflecting surfaces with zero sound absorption coefficients, thus not requiring any estimate or measurement for these surfaces. Numerical results show excellent comparison to experimental results for an actual plenum. The image model is also shown to be significantly more accurate than the standard large room diffuse field reverberant model.