The performance of coupled resonators in the presence of turbulent flows

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The performance of coupled resonators in the presence of turbulent flows

 

Author: Li, Wai-man
Title: The performance of coupled resonators in the presence of turbulent flows
Degree: M.Eng.
Year: 2005
Subject: Hong Kong Polytechnic University -- Dissertations
Turbulence -- Acoustic properties
Air ducts -- Acoustic properties
Resonators
Department: Dept. of Building Services Engineering
Pages: xii, 122, 12 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1810021
URI: http://theses.lib.polyu.edu.hk/handle/200/4473
Abstract: Helmholtz resonators are used to attenuate the unwanted sound in a variety of applications. This dissertation presents the findings on coupled resonators in the presence of turbulent flows. The sound attenuation of coupled resonators installed along a rectangular duct was studied experimentally at five air flow velocities: 0 m/s, 3 m/s, 5 m/s, 7 m/s, 9 m/s. Experiments demonstrate that the coupled resonators are tested under high turbulence intensities. Experiments confirm that the transmission loss of the coupled resonators generally drops with a higher velocity. The coupled resonators can perform effective sound attenuation for an air flow below 9 m/s. Negative troughs occur at the resonance frequency when the air flow velocity exceeds a certain value. The resonance frequencies of the resonators remain unchanged in the air flow conditions. The experimental results reveal that there is interaction between coupled resonators under different air flows. And the attenuation frequency bandwidth is widened by tuning the neck width of the resonators close to each other under both no flow and flow conditions.

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