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Multi-mode sound transmission in ducts with flow

Multi-mode sound transmission in ducts with flow
Multi-mode sound transmission in ducts with flow
Exhaust mufflers, large exhaust stacks, and turbofan engines are common examples of ducted noise. The most useful measure of the sound produced by these noise sources is the sound power transmitted along the duct. When airflow is present, sound power flow can no longer be uniquely determined from the usual measurements of acoustic pressure and particle velocity.
One approach to sound power determination from in-duct pressure measurement, and the one discussed in this paper, is to predict the relationship between the sound power and pressure based upon an assumed mode amplitude distribution. This paper investigates the relationship between acoustic pressure and power for a family of idealized source distributions of arbitrary temporal and spatial order. Incoherent monopole and dipole sources uniformly distributed over a duct cross-section can be obtained as special cases. This paper covers the sensitivity of the pressure–power relationship to source multipole order, frequency and, in particular, flow speed. It is shown that the introduction of flow in a hard-walled duct can have a substantial effect on the behavior of the pressure–power relationship for certain source distributions. Preliminary experimental results in a no-flow facility are presented in order to verify some of the main results.
0022-460X
523-544
Joseph, P.F.
9c30491e-8464-4c9a-8723-2abc62bdf75d
Morfey, C.L.
d5f9a8d0-7d8a-4915-a522-bf49dee111f2
Lowis, C.
42fc49d5-4244-43d4-a062-9c0bae92c2d1
Joseph, P.F.
9c30491e-8464-4c9a-8723-2abc62bdf75d
Morfey, C.L.
d5f9a8d0-7d8a-4915-a522-bf49dee111f2
Lowis, C.
42fc49d5-4244-43d4-a062-9c0bae92c2d1

Joseph, P.F., Morfey, C.L. and Lowis, C. (2003) Multi-mode sound transmission in ducts with flow. Journal of Sound and Vibration, 264 (3), 523-544. (doi:10.1016/S0022-460X(02)01205-1).

Record type: Article

Abstract

Exhaust mufflers, large exhaust stacks, and turbofan engines are common examples of ducted noise. The most useful measure of the sound produced by these noise sources is the sound power transmitted along the duct. When airflow is present, sound power flow can no longer be uniquely determined from the usual measurements of acoustic pressure and particle velocity.
One approach to sound power determination from in-duct pressure measurement, and the one discussed in this paper, is to predict the relationship between the sound power and pressure based upon an assumed mode amplitude distribution. This paper investigates the relationship between acoustic pressure and power for a family of idealized source distributions of arbitrary temporal and spatial order. Incoherent monopole and dipole sources uniformly distributed over a duct cross-section can be obtained as special cases. This paper covers the sensitivity of the pressure–power relationship to source multipole order, frequency and, in particular, flow speed. It is shown that the introduction of flow in a hard-walled duct can have a substantial effect on the behavior of the pressure–power relationship for certain source distributions. Preliminary experimental results in a no-flow facility are presented in order to verify some of the main results.

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Published date: 2003

Identifiers

Local EPrints ID: 10369
URI: http://eprints.soton.ac.uk/id/eprint/10369
ISSN: 0022-460X
PURE UUID: f157bf52-387f-4741-ba6d-8698549e6682

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Date deposited: 18 Jul 2005
Last modified: 15 Mar 2024 04:59

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Contributors

Author: P.F. Joseph
Author: C.L. Morfey
Author: C. Lowis

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