Research Of The Active Noise Control

The noise can produce a lot of harm to health of body and impact on people’sphysical and mental health seriously. To improve the quality of acoustic environmentand ensure the human health, active noise control method can be used to reduce noise,but the active noise control must satisfy two conditions: the same space location of thenoise source and the anti-noise source without delay. But the active noise control systemof practical application is impossible to satisfy these two conditions at the same timewhich may impact on noise reduction effect. Based on the problems which may occur inthe application process of the indoor active noise control system, the depth study of thenoise reduction effect on the active noise control of the different spatial position of thenoise source and the anti-noise source of delay was studied. On this basis, the nonlinearrelationship of the noise frequency and maximum sound source distance which achieveoverall noise reduction in the control region was proposed and the amplitude and phaseexpression of the superimposed signal of the noise source and delay anti-noise sourcewas derived, and a new method of noise reduction was proposed according to theexpression. Specific work and the results are as follows:①Noise from different sources and its strength is studied and compared with thestandard provisions of the state of noise value, the damage of noise to human health wasfound and certain method to suppress the noise should be taken,and to analysis differentmethods of noise control;②The noise reduction effect on the active noise control of the different spatialposition of the noise source and the anti-noise source was studied, through theoreticalanalysis and simulation studies prove that the noise reduction effect relate to the noisefrequency and the source distance, the greater the source distance, the greater theamplitude of noise within region and the greater the fluctuations of noise. Non-linearrelationship between noise frequency and maximum distance of the sound source whichachieve overall noise reduction in the control region was proposed, the greater thefrequency, the smaller the maximum sound source distance, and as the frequencyincreases, the maximum sound source distance is decreased rapidly at low frequency,but changed slowly at high frequency;③Verified by analyzing that the anti-noise source delay may generate peak noise which sound wave amplitude is greater than the original noise and adversely affect thenoise reduction effect. The amplitude and phase expression of the superimposed signalof the noise source and delay anti-noise source was derived by theoretical analysis,verified the theoretical correctness of the derived mathematical expressions and thefeasibility in the actual active noise control system. A new method to reduce the noisewas carried out according to the derived mathematical expressions, and the effect of thenoise reduction method was verified via simulation.