An Active Noise Control Approach for Attenuating Noise Above the Plane Wave Region in Ducts

Document type: Conference Papers
Peer reviewed: Yes
Full text:
Author(s): Martin Larsson, Kristian Nilsson, Sven Johansson, Ingvar Claesson, Lars Håkansson
Title: An Active Noise Control Approach for Attenuating Noise Above the Plane Wave Region in Ducts
Conference name: International Congress on Sound and Vibration, ICSV
Year: 2011
Publisher: International Institute of Acoustics and Vibration (IIAV)
City: Rio de Janeiro, Brazil
Organization: Blekinge Institute of Technology
Department: School of Engineering - Dept. of Electrical Engineering (Sektionen för ingenjörsvetenskap - Avd. för elektroteknik)
School of Engineering S-371 79 Karlskrona
+46 455 38 50 00
http://www.bth.se/ing/
Authors e-mail: mls@bth.se
Language: English
Abstract: In a narrow duct, a relatively simple single-channel feedforward ANC system may be used to attenuate noise propagating as plane waves. However, for ducts with larger dimensions the cut-on frequencies for one or several higher-order acoustic modes may be within the frequency range where ANC is applied. In such situations it is generally necessary to use a multiplechannel feedforward ANC system with several secondary sources, error sensors, and perhaps reference sensors. Such a system has a significantly higher complexity than a single-channel
ANC system. In this paper another approach is described. Instead of using a multiple-channel feedforward ANC system on a duct of large dimension, the idea is to divide the duct into several more narrow parallel ducts. In this way the complexity of the ANC system may be reduced.
In the experiments conducted for this paper, a duct was divided into two more narrow ducts. The noise propagating in each duct was controlled by a feedforward ANC system based on the leaky filtered-x LMS algorithm, where different reference- and error microphone configurations were used. The different configurations were compared to a configuration where the noise in respective narrow duct was controlled using a basic single-channel ANC system per duct. The results preliminary show that high attenuation of low-frequency noise in a duct of large dimension may be achieved using this approach.
Subject: Signal Processing\Active Noise and Vibration Control
Signal Processing\General
Keywords: Active Noise Control, ANC, Ducts, Plane Wave, Higher order modes
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