Performance Evaluation of a Module Configured Active Silencer for Robust Active Noise Control of Low Frequency Noise in Ducts

Document type: Researchreports
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Author(s): Martin Larsson, Sven Johansson, Lars Håkansson, Ingvar Claesson
Title: Performance Evaluation of a Module Configured Active Silencer for Robust Active Noise Control of Low Frequency Noise in Ducts
Translated title: Prestanda Evaluering av ett Modul Konfigurerat Aktivt Bullerundertryckningssystem för robust aktiv bullerundertryckning av lågfrekvent ventilationsbuller
Series: Research Report
Year: 2008
Issue: 6
ISSN: 1103-1581
Organization: Blekinge Institute of Technology
Department: School of Engineering - Dept. of Signal Processing (Sektionen för teknik – avd. för signalbehandling)
School of Engineering S- 372 25 Ronneby
+46 455 38 50 00
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Language: English
Abstract: Low noise level is an essential feature when installing ventilation systems today. Since the passive silencers traditionally used to attenuate ventilation noise tend to become bulky, impractical, and expensive when designed for low frequency attenuation, other solutions for the reduction of the low frequency duct noise often present in ducts are of interest. Active noise control (ANC) is a well known method for attenuating low frequency noise and much research has been performed to successfully apply ANC to duct noise. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is of highest importance to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. The work presented in this report is concerned with analysis of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system, and design of microphone installations which produce sufficient turbulence suppression while also meeting industrial requirements. These requirements are, for example, that the installations should be based on standard ventilation parts, and that they should be easily installed and maintained. Furthermore, results concerning the performance of an ANC system with different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO standard. The attenuation of duct noise achieved with ANC was approximately 15-25 dB between 50-315 Hz, even for airflow speeds up to 20 m/s.
Subject: Signal Processing\Active Noise and Vibration Control
Keywords: Signal Processing, Adaptive filters, Active Noise Control, Ventilation noise, Measurement noise, Turbulence
URN: urn:nbn:se:bth-00421