Active noise control in Helmet using Flexible Electret Loudspeaker

• Main Authors: Yu-Ting Yeh, 葉欲廷
• Other Authors: 林忠逸
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/44442756322311213492

碩士 === 國立中興大學 === 機械工程學系所 === 104 === Moving-coil loudspeakers are generally used as control speakers in active noise control (ANC) systems. A new kind of loudspeaker, flexible electret loudspeaker, is a plane type speaker and has a thickness of 0.1 cm only. It is not restricted to space and thus used as control speaker in an ANC system with a helmet in this study. A secondary path of the ANC helmet system can be time varying. Thus, the technique of an ANC system with online secondary path modeling is adopted to solve the problem. Moreover, NLMS algorithms with exponential decay step-size (EDSS), reduced optimal variable step-size (ROVSS), or constant step-size (CSS) are used for ANC controller and secondary path modeling to adjust filter coefficients in the helmet ANC experiments. Experimental results show that the method of ROVSS is the most effective way in terms of speed and accuracy of the secondary path modeling and level of noise reduction of the ANC performance among these three methods.