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Journal of Sensors
Volume 2016, Article ID 5185242, 9 pages
Research Article

Characteristics of Relocated Quiet Zones Using Virtual Microphone Algorithm in an Active Headrest System

Department of Embedded Systems Engineering, Incheon National University, 119 Academy-ro, Yeonsu-gu, Incheon 406-772, Republic of Korea

Received 30 January 2016; Accepted 30 March 2016

Academic Editor: Yurong Qian

Copyright © 2016 Seokhoon Ryu and Young-Sup Lee. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


This study displays theoretical and experimental investigation on the characteristics of the relocated zone of quiet by a virtual microphone (VM) based filtered-x LMS (FxLMS) algorithm which can be embedded in a real-time digital controller for an active headrest system. The attenuation changes at the relocated zones of quiet by the variation of the distance between the ear and the error microphone are mainly examined. An active headrest system was implemented for the control experiment at a chair and consists of two (left and right) secondary loudspeakers, two error microphones, two observer microphones at ear positions in a HATS, and other electronics including a dSPACE 1401 controller. The VM based FxLMS algorithm achieved an attenuation of about 22 dB in the control experiment against a narrowband primary noise by the variation of the distance between the ear and the error microphone. The important factors for the algorithm are discussed as well.