本研究利用前饋（Feedforward）、反饋（Feedback）和複合（Hybrid）三種架構實現耳機的主動式噪音控制。
第一步是由電聲模型設計前饋、反饋控制器，模擬演算法的效果和可實現性。第二步是建立實際的耳機模型，使電聲模型更為精確。
在控制器的部分，前饋和反饋分開設計。其中前饋使用模型匹配（Model Matching）的方法，由外耳麥克風接收噪音，經過控制器處理後產生其反向波形在耳機內和噪音互相抵消，達到噪音降低的效果。而反饋則用最佳化控制中的線性二次高斯控制（Linear Quadratic Gaussian Control），其設計受到二次成本函數的限制，可自行調配出最想要的結果。複合則是將兩者的結構串接，使得噪音控制的效果更大。
最後以DSP用不同種類的噪音測試此控制方法的效果，可在200~2kHz頻段中降低噪音10~15dB。

This research mainly focuses on the implement of three structures which includes feedforward, feedback and hybrid applied to active noise control of headset.
First design the feedback and feedforward controllers with electroacoustic model and simulate the effect and realizability of the algorithm. The second step is to establish the actual headset model to make electroacoustic model more accurate.
In the part of the controllers, we design the feedback and feedforward controllers separately. In feedforward, model matching method is applied. Noise from the external-ear microphone is processed by the controller to produce its reverse waveform to cancel itself in the headset which can achieve noise reduction. In feedback, we use linear quadratic Gaussian control, one of the most optimal control. Its design is constrained by the quadratic cost function. We can adjust the parameters for the most desired result. Hybrid concatenates the two structures above to enhance the effect of noise control.
At last, DSP is applied to test the noise reduction effect with different kinds of noise. It can reduce 10-15dB broadband noise in 200-2kHz.

1 Shaw, E. A. G. and Thiessen, G. J. “Acoustics of circumaural earphones,” Journal of the Acoustical Society of America, 34(9), 1233-1246 (1962).
2 Simshauser, E. D. and Hawley, M. E. “The noise canceling headset - an active ear defender,” Journal of the Acoustical Society of America, 27, 207 (1955).
3 Hawley, M. H. “Acoustic interference for noise control,” Noise Control, 2, 61-63 (1956).
4 Shaw, E. A. G. and Thiessen, G. J. “Acoustics of circumaural earphones,” Journal of the Acoustical Society of America, 34(9), 1233-1246 (1962).
5 Tseng, W. K., Rafaely, B. and Elliott S. J. “Combined feedback-feedforward active
control of sound in a room,” Journal of the Acoustical Society of America, 104(6), 3417-3425 (1998).
6 Bai, M. S. and Lee, D. “Implementation of an active headset by using H∞ robust control theory,” Journal of the Acoustical Society of America, 102(4), 2184-2190 (1997).
7 Rafaely, B. “Active control of sound”. PhD thesis, University of Southampton, UK (1997).

8 Frid, O. “Active noise reduction in earphone by feedback with system model uncertainty”. MSc thesis, Tel-Aviv University, Israel (1999).
9 B. Sinopoli, L. Schenato, M. Franceschetti, K. Poolla, and S. Sastry, “An LQG optimal linear controller for control systems with packet losses,” IEEE Conference on Decision & Control, Seville, Spain, 458–463 (2005).
10 Bai, M. S. and Hsu W. C. “Adaptive filtering with applications in barge-in handling, nonlinear echo cancellation and active headsets,” 20-24 (2011).
11 Roure, A. “Self-adaptive broadband active sound control system”. Journal of Sound and Vibration, 101, 429-441 (1985).
12 Widrow B. and Stearns S.D., Adaptive signal processing, Prentice Hall, NY (1985).
13 A. J. Brammer, G. J. Pan, and R. B. Crabtree, “Adaptive feedforward active noise reduction headset for low-frequency noise,” Proceedings of the ACTIVE 97 Conference, Budapest, Hungary, pp. 365–372 (1997).
14 B. Rafaely, ‘‘Active noise reducing headset—an overview,’’ Proceedings of the Internoise 2001 Conference, August 2001, The Hague, Holland, pp. 589–598 (2001).
15 P.P. Vaidyanathan, Multirate Systems and Filter Banks, Prentice-Hall, 100-133 (1993).
16 Thiele, A. Neville, "Loudspeakers in Vented Boxes," Proceedings of the Institute of Radio Engineers, Australia, 22(8), pp. 487-508 (1961).
17 R H Small, “Direct-Radiator Loudspeaker System Analysis,” Journal of the Audio Engineering Society, 20(5): 383–395 (1972).
18 Rafaely, B. and Jones, M., “Combined feedback-feedforward active noise-reducing headset - the effect of the acoustics on broadband performance,” Journal of the Acoustical Society of America, 112 (2002).
19 Stephen Boyd, Linear Dynamical Systems Lecture 4 Continuous time linear quadratic regulator [Electronic version], 1-28 (2008).
20 M. R. Bai, “Linear System Theory and Design”, Lecture Notes Chap.8 (2015).
21 M. R. Bai, 工程聲學, 全華, chap.5 1-17 (2008).
22 K. A. Lee, W. S. Gan and S. M. Kuo, Subband Adaptive Filtering: Theory and Implementation, Wiley, New York (2009).
23 Simon Haykin, “Adaptive Filter Theory,” Prentice Hall (2002).
24 Juang J.-N. and Pappa R. S. “An Eigensystem Realization Algorithm for Modal Parameter Identification and Model Reduction,” Journal of Guidance, Control, and Dynamics. 8 (5) (1985).
25 Giovanni L. Sicuranza and Alberto Carini, “Filtered-X NLMS algorithm with compensation of memoryless nonlinearities for Active Noise Control,” EUSIPCO, (2008).
26 P.P. Vaidyanathan, Multirate Systems and Filter Banks, Prentice Hall, 100-133 (1993).
27 Doyle, J. C., Francis, B. A., and Tannenbaum, A. R., Feedback Control Theory, Maxwell MacMillan Canada Toronto (1992).