Adaptive control on sound transmission through apertures at low frequence

• Main Authors: Wang,Liang-Jong, 王亮中
• Other Authors: Chen,Kuo-Tsai
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/91242518698841073215

碩士 === 國立臺灣大學 === 造船工程學系 === 81 === In noise control engineerihg , the passive control techni -que is always popularly used to improve noise problem . And the above passive noise control technique is almost using the combination of panels with absorbing materials to protect the transmission in duct by changing its cross-section . Generally , passive noise control technique doesn't have good control effectiveness on noise at low frequency and also appears very uneconomically . For the case of rectangular aperture , using absorbing material also can greatly reduce high-frequency noise . But it still can't provide an effective control method to low -frequency noise . Therefore , this paper would like to concentrate the study of adaptive control system design and it' s effectiveness to noise control on sound transmission through apertures at low frequency . In discussing the above adaptive control system , it's main acoustic logic is using a FIR filter with adaptively adjusting it's parameters to produce an output signal that will make controllable sources to generate an acoustic filed to pro -tect the noise tranemission being controlled . Hence this study would like to set up an experiment of active control on pure tonal noise of low frequency by matching error signal transmitting from monitoring microphone after aperture with the parametric operation on system by least square method . Finally , the results of active control experiment on noise in aperture shows that the greastest acoustic reduction of noise transmission in aperture by 15 decibels would be obtained when the adaptive control technique building in this paper is used .