本論文研究目的，是建構出一套應用時間反轉法與微麥克風陣列於3G手機上之抗噪系統。時間反轉法(Time reversal method, TRM)為基礎的聲源分離與辨識技術，TRM主要是利用回傳時間反轉之聲波訊號，藉由聲波之互易性原理(Principle of reciprocity)及線性波動方程式的不變性，補償因多重路徑傳遞與傳遞介質不均勻所造成的訊號失真，使訊號得以聚焦於原聲源位置。近年來廣泛應用於光學、超音波、非破壞檢測及水下通訊領域。本研究主要分成理論推導、數值模擬與實驗分析。理論推導中，包含TRM理論推導與環境脈衝響應函數求解。如何準確預估出環境脈衝響應函數，是本研究重點。數值模擬則是利用不同環境條件參數，模擬出TRM聚焦的效果，並使用相關度係數與訊雜比作為量化分析。在實驗分析部分，則是使用微麥克風陣列進行量測，並於時間域下對聲源進行分離與辨識。經過實際測試，可以消除由非主要聲源所產生的雜訊干擾，提高主要聲源訊號之訊雜比與相關性係數。證實本研究所建構的抗噪系統是有成效的，提升訊雜比幅度可達到目標值5dB~10dB，大幅提升聲音的品質與清晰度。

The purpose of this paper is to construct a noise control system in the 3G cell phones that combines time reversal method and MEMS array microphones. Time reversal method (TRM) is based on principle of reciprocity of sound by propagating of a reversal signal in time series to compensate distortion due to path effect in propagation and to focus the signal at origin. In recent years, the technique has been applied in optics, ultrasound and underwater acoustic communication. This research mainly divides into theoretical derivation, numerical simulation and experiment. Theory derivation includes TRM theory and solution of impulse response function of the path. The key point of this research is how to estimate accurately the impulse response function. Numerical simulation is to verify the effect of focusing by using TRM in the different environmental conditions and parameters. Also, it uses correlation coefficient and signal-to-noise ratio to analyze the result of TRM. In the experiment, MEMS array microphones are used to receive the signals. Then, the source signal is separated from the received signals in time domain. As the results of the experiment, the technique is to separate a specific source from a combination signal of multiple sources and to reduce noise effectively. The results indicate that TRM increases value of the correlation coefficient and signal-to-noise ratio of the source of interest. The results also confirm that the anti-noise system in this research is effective to enhance the signal-to-noise ratio by 5dB to 10dB, which significantly enhances the sound quality and clarity.

1.D. R. Jackson and D. R. Dowling, “Phase conjugation in underwater acoustics”, J.A.S.A. 89, pp. 171-181, 1991.

2.D. Caesarea and M. Fink, “Time Reversal of Ultrasonic Field, PartIII: Theory of the Closed Time-Reversal Cavity”, IEEE Trans. UFFC., 567-578, Sep 1992.

3.D. Caesarea and M. Fink, “Focusing with plane time-reversal mirrors: an efficient alternative to closed cavities”, J.A.S.A., 2373-2386, Oct 1993.

4.N. Chakroun, M. Fink, and F. Wu, “Time reversal processing in ultrasonic non destructive testing”, IEEE Trans. Uffc., 1087-1098, 1995.

5.J. de Rosny and M. Fink, “Overcoming the diffraction limit in wave physical using a time-reversal mirror and a novel acoustic sink”, Physical Review Letters, Vol.89(12), 124301, 2002.

6.G. Lerosey, J. de Rosny, A. Tourin and M. Fink, “Focusing beyond the diffraction limit with far-field time reversal”, Science, 315, 1120-1122, 2007.

7.S. G. Conti, P. Roux and W. A. Kuperman, “Near-field time-reversalamplification”, J.A.S.A, Vol.121(6), 3602-3606, 2007.

8.林明宏, “時間反轉陣列之聚焦解析度分析”, 國立台灣大學工程科學及海洋工程研究所碩士論文, 中華民國九十五年五月。

9.邱永盛, “運用被動相位共軛等化理論於淺海內波環境之通訊成效分析”, 國立台灣大學工程科學及海洋工程研究所博士論文, 中華民國九十七年六月。

10.涂季平, 謝羽豪, 李新立, “時反法于海下通訊與定位之研究現況,” 海洋及水下科技季刊, 十八卷, 第四期, 2008。

11.Bo-Hsien Wu, Gee-Pinn Too, Sony Lee, “Simulation of Audio Signal Separation by Time Reversal Method”, Journal of the Acoustical Society of America. (In press)

12.Jianmin Miao, Rongming Lin, Longqing Chen, Quanbo Zou, Sin Yee Lim, Suan Hee Seah, “Design considerations in micromachined silicon”,Microelectronics Journal 33, 21-28, 2002.

13.Peter V. Loeppert, Sung B. Lee,“SiSonicTM-The First Commercialized MEMS Microphone”, Solid-State Sensors, Actuators and Microsystems Workshop, 2006.

14.黃士韋, “微機械陣列麥克風之System-on-chip設計”, 國立交通大學機械工程研究所碩士論文, 中華民國九十二年六月。

15.林振邦, “微機械麥克風之最佳化設計及其陣列於3D聲場重建之實現”, 國立交通大學機械工程研究所碩士論文, 中華民國九十三年六月。

16.沈世雄, “新式微機電濾波器於助聽器應用之研究”, 國立陽明大學醫學工程研究所博士論文, 中華民國九十三年六月。

17.李昇翰, “可適應性噪音消除系統研究”, 高苑科技大學電子工程研究所碩士論文, 中華民國九十七年七月。

18.Sazzadur Chowdhury, M. Ahmadi, G. A. Jullien, W. C. Miller, “A MEMS Implementation of an Acoustical Sensor Array”, IEEE International
Symposium on Circuits and Systems, Vol. 2, p II273-II276, 2001.

19.Humphreys Jr., William M., Shams, Qamar A., Graves, Sharon S., Sealey, Bradley S., Bartram, Scott M., Comeaux, Toby, “Application of MEMS microphone array technology to airframe noise measurements”, Collection of Technical Papers - 11th AIAA/CEAS Aeroacoustics Conference, Vol. 4,
p 2566-2585, 2005.

20.Tsubaki K., Yamanaka H., Kitada K., Komoda T., Koshida N., “New ultrasonic image sensing by nanocrystalline porous silicon ultrasonic emitter combined with a condenser microphone array,” Proceedings of the 12th International Display Workshops in Conjunction with Asia Display, p 2011-2014, 2005.

21.蔡信宏, “水下超音波相移陣列系統之研發及其應用”, 國立台灣海洋大學電機工程研究所碩士論文, 中華民國九十五年七月。

22.何其恩, “水下壓電式步進相移超音波陣列發射接收影像系統之研發及其應用”, 國立台灣海洋大學電機工程研究所碩士論文, 中華民國九十六年七月。

23.Bing Li, Dian-Ge Yang, Lin Shao, Xiao-Min Lian, “Development of Acoustic Video Camera System Based on Binocular Vision and Short-Time Beamforming”, International Congress and Exposition on
Noise Control Engineering, October 2008.

24.Reinhold Haeb-Umbach, Sven Peschke, Ernst Warsitz, “Adaptive Beamforming Combined with Particle Filtering for Acoustic Source Localization “, International Conference on Spoken Language Processing, October 2004.

25.Jean-Marc Valin, François Michaud, Jean Rouat, “Robust localization and tracking of simultaneous moving sound sources using beamforming and particle filtering, “ Robotics and Autonomous Systems, Volume 55,Issue3, Pages 216-228, 31 March 2007.

26.Gunnar Heilmann1, Dirk Döbler2 , “Improving the Time / Spatial Resolution Capabilities of Beamforming in the Time Domain using Zeropadding”, International Congress and Exposition on Noise Control
Engineering, October 2008.

27.P.A. Nelson, S.H. Yoon., Eatimation of acoustic source strength by inverse methods Part I, conditioning of the inverse problem, Sound and Vibration
233 (4) (2000) 643-668.

28.S.H. Yoon, P.A. Nelson., Eatimation of acoustic source strength by inverse methods Part II, experimental investigation of methods for choosing regularization parameter, Sound and Vibration 233 (4) (2000) 669-705.