Active Control on the Acoustic Fields in Duct Using the Wall-Vibration Induced Acoustic Sources
Date Issued
2009
Date
2009
Author(s)
Chen, Tsung-Chih
Abstract
There are two techniques in noise control,which are passive and active noise control.This thesis is to provide another approach to active noise control(ANC).It is to use a piezoelectric transducer(PZT) to excite the duct wall.The wall-vibration induced feedback sound wave can combine with primary noise to reduce the downstream sound pressure.Accordingly,only a duct and a piezoelectric tr-nsducer are wanted in this approach.Thus the cost and the space required for the apparatus to be wanted are saved much more. In experiment,we use a FIR digital filter as the main structure of the control system and meanwhile take a single-frequency or a dual-frequency signal as the reference input directly produced by a function generator.Weighting coefficients of the digital filter are adjusted by using LMS algorithm in order to achieve the best performance.Besides,the sound radiation by vibrating an infinite cylindrical shell will be analyzed. The result of this study shows great attenuation of downstream sound pressure level by about 40 dB will be obtained at some frequencies.Similar situation occurs for dual frequencies at which greater radiation from duct wall exists,the attenuation of downstream sound pressure levels by about 15~35dB is obtained.The actuality as discussed can demonstrate it is feasible to use wall-vibration induced source to adaptively active control on the sound transmissi-n in a circular duct.
Subjects
Active control
Wall-vibration induced acoustic sources
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-R96525067-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):895255199d6124638c7002b5a8860bd7