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Title:

Numerical Investigation of Acoustic Impedance of Perforated Tubes

Accession Number:

01054334

Record Type:

Component

Availability:

Institute of Noise Control Engineering

Iowa State University, 210 Marston Hall
Ames, IA 50011-2153 United States

Abstract:

This paper describes how perforated tubes in mufflers and silencers have been modeled by the transfer impedance approach since 1978. Based on experiments performed since then, several alternative empirical formulas have been proposed that represent the acoustic impedance of perforates under different flow conditions. The impedance formulas are obtained based on the condition that the tube has a uniform hole-diameter and hole-pattern. In general the empirical formulas work well in most cases. However, there are some discrepancies in situations where the acoustic behavior of the perforated element can be influenced by the size of the hole and locations along the tube. The objective of this paper is to study the numerical model the actual geometry and location of the holes on the perforated tubes using the boundary element method (BEM) and to compare the results with empirical formulas. In order to overcome the enormous task of modeling the details of each hole on the perforated tube, a newly developed substructuring BEM method4 is used. A small section of the perforated tube which consists of identical number of holes and pattern is modeled and is used as a template for the repeating substructures. Since the geometry of repeating substructures remains the same, the impedance matrix does not need to be re-calculated for each substructure. The resultant impedance matrix of the entire muffler can be obtained by an impedance matrix synthesis procedure. Subsequently, the transmission loss (TL) of the muffler can be calculated based on the resultant impedance matrix.

Monograph Accession #:

01054353

Language:

English

Corporate Authors:

Institute of Noise Control Engineering

Iowa State University, 210 Marston Hall
Ames, IA 50011-2153 United States

Transportation Research Board

500 Fifth Street, NW
Washington, DC 20001 United States

Authors:

Balasubramanian, D
Wu, T W
Cheng, C Y R

Editors:

Burroughs, Courtney B
Maling, George C

Pagination:

pp 507-514

Publication Date:

2004

Conference:

Noise-Con 04. The 2004 National Conference on Noise Control Engineering

Location: Baltimore Maryland, United States
Date: 2004-7-12 to 2004-7-14
Sponsors: Institute of Noise Control Engineering; Transportation Research Board

Media Type:

CD-ROM

Features:

Figures (10) ; References (11) ; Tables (1)

Subject Areas:

Energy; Environment; Highways; Vehicles and Equipment; I15: Environment; I91: Vehicle Design and Safety

Files:

TRIS, TRB

Created Date:

Jul 25 2007 1:22PM