Study On Active Control Noise Technique For Engine Exhaust Noise

Engine exhaust noise is an important source of the engine noise. Although the muffler technique has been matured, it has inevitable limitations. The active control noise (ANC) technique can offset the limitations of muffers, which eliminate the noise by interference of sound wave under the help of Digital Signal Processing technique. ANC technique has many merits, and has become a hotspot in noise reigning region of engine exhaust in recent years. The applications of active control noise technique in reducing the engine exhaust noise will be mainly researched in this paper.First of all, the concept, principle, development and the state of art of active control noise technique are introduced. Then the framework and algorithm of ANC are analyzed and researched in detail and get obviously effect of reducing noise form simulations results made by using MATLAB.An active noise control system based on Digital Signal Processing technique is developed.It possesses double CPU structure, DSP and singlechip. And LMS algorithm is realized on DSP and the operation status parameters from ECU are processed in singlechip, and than decide the optimal algorithm, parameters and working mode to make system work in optimal mode. The ANC system has forward and feedback framework and is designed in modules, which will be helpful for updating, extending and testing. The system can be used to decide the optimal algorithm parameter and work mode in vary working condition. The working frequence of controller, the channel gain of ADC and DAC, transmission mode of data and the type of filter and microphone can be modulated by manual or automatic mode. We can find the optimal mode and algorithm by manual control, then use the singlechip modulate automatically after get the determined relation between operation parameters and optimal control mode.Finally experiments on interference noise elimination technology of sound wave have been carried out. The different frequency sine wave, as well as the exhaust noise signal which under typical engine operating mode, were used to realize interference elimination of sound wave in entire sealed noise elimination room under the control of computer. The analysis results indicated that interference noise elimination technology has obvious effects on noise reducting.