Research And Implementation Of Indoor Noise Reduction ANC System

With the continuous development of economy and society,urban traffic noise is also increasing.In 2018,79.8% of municipalities directly under the central government and provincial capital cities failed to meet the national noise standard at night.Long term exposure to noise environment will cause digestive system and nervous system damage.In daily life,noise barrier is mainly used for traffic noise,which has a significant effect on high-frequency noise reduction.However,this thesis finds that low-frequency is the main part of traffic noise.The ideal way to control low-frequency noise is to use the principle of sound wave superposition to generate sound waves with the same amplitude and opposite phase as the noise source to eliminate noise in space.In order to solve the problem of secondary path identification in the indoor noise elimination system,this thesis proposes a variable step size active noise control(ANC)system based on the least mean square(LMS)algorithm.In order to improve the convergence speed in the actual noise environment,the modeling filter uses variable step momentum LMS algorithm to update the weight coefficient of the secondary path.Simulation results show that the algorithm improves modeling accuracy,steady-state performance,convergence speed and noise reduction by 14.3%.At the same time,in order to solve the problem of high computational complexity in the indoor noise cancellation multi-channel system,this thesis proposes a mixed error multi-channel ANC system.The mixed error multi-channel ANC system takes the sum of all error microphone outputs as a mixed error signal,and uses the mixed error signal to update the weight of the control filter.The simulation results show that under the premise of ensuring the stability of the system,the mixed error type 2-channel active noise control system reduces the computational complexity by 67.9% compared with the complete 2-channel active noise control system.This article is to solve the problem that the ANC system runs slowly on the Field Programmable Gate Array(FPGA)development board,which in turn affects the noise reduction performance of the system.Respectively identify the variable-step ANC system and the mixed error multi-channel ANC system on the secondary path of the momentum LMS algorithm,and establish an indoor noise reduction ANC system experimental platform.The article will focus on the optimal design of the hardware circuit design of each module in the ANC algorithm system and use Verilog HDL to complete the circuit design of the indoor noise reduction ANC system,then load the code onto the Xilinx XC7Z015-2clg485 I development board for experiments.The experimental results show that the variable-step ANC system based on the online identification of the secondary path of the momentum LMS algorithm can reduce the noise by up to 14 d B.Multi-channel ANC systems based on mixed errors can reduce noise by up to 10 dB.