A Digital Hybrid Active Noise Reduction Earphone System

With the advancement of science and technology and the development of industry,the problem of noise pollution has become more and more prominent,and its impact on people's physical and mental health has become more and more serious.Seeking a quiet environment and obtaining clear voice messages are becoming more people's living standards.Therefore,active noise control technology emerged at the historic moment,which is widely used in noise reduction headsets,ships,automobiles and other scenes.At present,most of them are dedicated noise reduction chips,such as Qualcomm's CSR8675 and QCC5100,ams' AS3460,ADI The company's ADAU1787 includes BES2300HP3,BES2500 Z,etc.of the emerging domestic Hengxuan company in recent years.However,the current best active noise reduction chips basically come from abroad.In recent years,foreign technology monopolies in many aspects have forced us to speed up the pace of localization of core technologies,especially technologies and products used in the military industry.This paper implements a digital hybrid active noise reduction headset based on a common platform,and its method is an improved FXLMS feedforward and feedback hybrid noise reduction algorithm.Through simulation and experiments,it is found that in the process of pre-feedback hybrid noise reduction,the noise reduction effects of the feedforward and feedback parts will restrain each other,so that during adaptive hybrid noise reduction,the filter coefficients of the feedforward and feedback will converge in the opposite direction.In view of this situation,this paper improves its structure on the traditional algorithm,removes the coupling relationship between feedforward and feedback,and superimposes them to obtain hybrid noise reduction after their respective noise reduction.In addition,in the actual application process,after the feedforward and feedback coefficients are converged for the first time,the coefficients can be fixed,and then the noise can be reduced directly,thereby eliminating the time to converge the coefficients.In addition,this noise reduction headset is based on a general MCU platform,which realizes the controllable active noise reduction technology.In this paper,the above-mentioned improved algorithm is implemented on the general platform STM32F429,and the entire noise reduction headset system is realized.Under 1.6kHz bandwidth white noise,the noise reduction results show that the average noise reduction of one-third octave in the 63Hz?1kHz bandwidth reaches 21 dB,and the maximum noise reduction depth reaches 46 dB at 126 Hz,which illustrates the noise reduction scheme proposed in this paper.The feasibility of the project and a reference case for engineering realization are given.