本文探討長直圓管模型中加入寬度0.5cm~5cm之狹縫裝置，其對頻率範圍200Hz~700Hz下，管內聲場分佈造成之可能影響。針對是否加入狹縫裝置、是否調整參考麥克風訊號強度，以及聲源之位置是否位於圓管中等不同條件下之實驗，比較其結果，觀察狹縫裝置所造成之影響，並找出狹縫裝置有效之寬度及頻率，證明添加狹縫裝置的確能有效使管道內之聲壓值降低。再進行主動式噪音控制方法，以TMS320C32的數位訊號處理卡執行LMS演算法，輸出訊號至第二聲源以發出能有效降低主聲源之噪音，由此實驗結果比較狹縫裝置與主動式噪音控制之效果優劣。最後，將兩者結合以得到最佳之減噪效果，並探討影響實驗結果之原因。

　　In this paper, the possible influences on acoustic distribution of a cylindrical tube with a slit device are discussed. The experimental results were compared under different conditions which are: (1)adding slit devices or not; (2)adjusting the intensity of the reference microphone or not; (3)adding sound source into the tube or not. Then, the effects of slit device and the effective width and frequency of slit device are discussed. The discussions indicate that slit devices can lower the in-tube sound pressure effectively. Furthermore, Active Noise Control with LMS algorithm is used to generate the output signals of the second sound source in order to cancel the noise of the original sound source. Finally, the experimental results of applying slit devices and active noise control(ANC) alone or together are compared. The results are discussed in details.

[1]P.Lueg，“Process of silencing sound oscillations”U.S. Patent，NO.2043416，1936
[2]M.A.Swinbanks，“The active control of sound propagation in longducts”Journalof Sound Vibration，27(3)，pp.411~436，1973
[3]J.H.B.Pools,and H.G.Leventhall，“An experimental study of‘Swinbanks’methodof active attenuation of sound in ducts”Journalof Sound Vibration，49，pp.257~266，1976
[4]C.F.Ross，“An adaptive digital filter for broadband active soundcontrol”Journal of Sound Vibration，80，pp.381~388，1982
[5]J.C.Burgess，“Active adaptive sound control in a duct : A computersimulation”J.Acoustic.Soc.Am 70(3)，1981
[6]P.A.Nelson,A.R.D.Curtis,and S.J.Elliott，“Quadratic optimizationproblems in the active control of free and enclose soundfields”Proceedings of the Institute of Acoustics，pp.45~53，1985
[7]P.A.Nelson,A.R.D.Curtis,S.J.Elliott,and A.J.Bullmore，“Theminimum power output of free point sources and the active control ofsound”Journal of Acoustics，116(3)，pp.397~414，1987
[8]L.J.Eriksson,M.C.Allie,and R.A.Greiner，“The selection andapplication of an IIR adaptive filter for use in active sound attenuation”IEEE Transactions on acoustics,speech,and signal processing ASSP-35，No.4，1987
[9]B.Friedlander,and Boazporat，“Adaptive IIR algorithm base onhigh-order statistics”IEEE，ASSP-37，No.468，1987
[10]M.Winberg,S.Johansson,and I.Claesson，“An active headset basedon hybrid active noise control technology”The 2001 internationalcongress and exhibition on noise control engineering The Hague，TheNetherlands，2001 August 27-30
[11]B.Rafaely，“Active noise reducing headset – an overview” The 2001international congress and exhibition on noise control engineering TheHague，The Netherlands，2001 August 27-30
[12]K.Yanagimoto,T.Ito,S.Sakamoto,R.Ichimiya,andK.Tanifuji，“Active noise control using slit resonators in cylindrical duct edge”The 2001 international congress and exhibition on noise controlengineering The Hague，The Netherlands，2001 August 27-30
[13]A.Sadamoto,Y.Murakami,and S.Masuda，“Attenuation of soundincluding higher-order mode waves in circular duct using a narrow sliton the duct wall”Transactions on JSME vol.59， No.568，pp.256-261，in Japanese 1993
[14]K.Yanagimoto,T.Ito,and R.Ichimiya，“Radition from ventilationaperture with circular thin air layer setting up machinery wall”Transactions on JSME，vol.66，No.64620752081，Jun，in Japanese2000
[15]Y.Honda,Y.Ohta,and H.Matsuhisa，“Reduction of sound powerradiated into free field by passive silencers” VSTech 97’，pp.79-82，1997
[16]Sen M.Kuo,and Dennis R.Morgan，“Active Noise Control Systems –algorithms and DSP implementations”
[17]潘政佳，“穿透平板噪音之主動結構噪音控制”，國立成功大學造船暨船舶機械工程研究所碩士論文，2001
[18]葉志明，“狹縫裝置應用於圓管內主動噪音控制之研究 ”，國立成功大學造船暨船舶機械工程研究所碩士論文，2002