Design And Implementation Of Active Noise Control System On Pipes Fan

There are various pollution in the environment where people live,and noise pollution is one of them which people pay more and more attention to.Fan noise is an important component in several sources of noise pollution,which is widely distributed around many occasion,such as vehicle exhaust,underground ventilation,and indoor ventilate.The aerodynamic noise is the main noise source in the fan noise,which contains two types of noise: discrete noise and broadband noise.For the discrete noise which has narrowband characteristic and the low and middle frequency bands in broadband noise,the traditional passive noise control methods are hard to achieve good results,so this paper plans to choose the pipeline for research and use active noise control(ANC)method.This paper mainly aim at the frequency mismatch problem in the fan noise and uses the improved ANC methods to test.First,use software simulation to verify the efficiency of the methods.Then,do the real noise control experiment,which use DSP as the main controller,to verify the algorithms.Finally,build a active noise control system used for l ow frequency narrowband fan noise control.The paper focused on three aspects: fan platform design,hardware design,and DSP software design.1)Fan platform design.First,analyze the generating mechanism and the frequency response characteristic of the fan noise.Then,to deal with the wind pressure problem in the sound collection,the paper do a study on how to choose a pipeline and where to place the fan and the microphone.Verify the fan noise character and get the fan noise frequency mismatch condition.2)Hardware design.Aim at the disadvantage that the mainstream platform don't have enough audio interfaces,this paper design a hardware system contains AIC23 B audio chip and other peripheral based on the DSP minimum system board.Then,finish the plate welding and hardware test work.3)DSP software design.This paper analyzes the disadvantages in the system running and testing.To improve the stability and utility of the system,plan to increase automatic fundamental frequency identification module and divergent detection module.At last,this paper combines software,hardware and platform design to verify the algorithm and function.Do the utility test of the improved module,performance test of the frequency mismatch algorithm,and simulation active noise control testing of the fan noise separately.Based on the result of the experiment,analyze the achievement and the problem in the experiment and outlook the next step work.