Generalised prediction methods for flow-generated noise produced by multiple in-duct elements

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In recent years, several studies have sought to develop a generalised prediction method for flow-generated noise that is produced by the interaction of multiple elements in the airflow duct of an air-conditioning system. The prediction methods for single or multiple in-duct discontinuities are based on the assumption that there is a constant of proportionality between the fluctuating drag force and the steady drag force that acts on the flow spoilers. To develop a prediction method for multiple in-duct discontinuities, the concept of partially coherent sound fields is adopted to formulate the sound powers that are produced by the interaction of multiple in-duct elements at frequencies both below and above the cut-on frequency of the lowest transverse duct mode. An interaction factor is defined as the result of a simple relationship between the sound power that is due to the interaction of multiple in-duct elements and the sound power that is due to a single in-duct element. The method has been found to agree well for two in-duct elements with experimental studies. This paper introduces the recent developments in the prediction methods, and discusses the problems that are encountered in the development of the technique.
Original languageEnglish
Pages (from-to)23-26
Number of pages4
JournalHKIE Transactions Hong Kong Institution of Engineers
Issue number4
Publication statusPublished - 1 Jan 2005


  • Air Duct
  • Flow-generated Noise
  • Generalised Prediction Method
  • In-duct Elements
  • Sound Power Level

ASJC Scopus subject areas

  • Engineering(all)

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