Research On Active Noise Reduction Headrest Device

Active noise reduction headrest system can be generally mounted in the seat positions of pilots and passengers of airplanes,cabins and automobiles,to eliminate noise interference and improve the comfort for human beings.In this paper,a SAIC Maxus G10 is adopted as the research object and a set of active noise reduction headrest equipment is designed to attenuate the low-frequency noise inside the vehicle.The contents include the following aspects:Firstly,the paper investigates some adaptive algorithms,including LMS algorithm,normalized LMS algorithm,variable step size algorithm and FxLMS algorithm,and the characteristics of the algorithms are analyzed and compared with each other.Secondly,an active noise reduction headrest system is set up in the laboratory.The feedforward and feedback structure of the active noise controller,the FIR filter and IIR filter are explored.By comparing the control results,the feedback structure and IIR filter are adopted in the active noise headrest equipment.Both single-frequency and multi-frequency noise are used as noise sources to verify the control performance of the controller and a satisfactory noise reduction is achieved.Thirdly,in order to install the active noise reduction equipment on an effective position inside the car,the modal characteristics of the interior acoustic cavity of the car are analyzed.Based on Maxus G10 above and the modal analysis theory of interior acoustic cavity,a systemic model is built and the acoustic modal calculation of the cavity is finished via finite element analysis.According to the modal distribution of the cavity in the interested frequency band,the installation of active noise reduction headrest is reasonably arranged.Finally,the active noise reduction headrest system is verified in the automobile.This part firstly introduces the selection of system hardware and the design of control software of noise cancelling system.Then the headrest equipment is installed on the car seat for road test.The experimental results show that the equipment achieves obvious noise reduction.At the same time,since the equipment is cheap and well developed,it is promising to apply it in the engineering.