Research On Active Noise Cancelling Headphones Based On DSP

There is a lot of noise in our daily life environment,and noise always affects people's work and rest.Therefore,how to effectively reduce the impact of noise has become a major concern.At present,industries such as automobiles,portable wearable devices,and home appliances have begun to take noise control as a key technical problem to overcome.Active noise reduction has become a hot research topic at present because of its excellent applicability and excellent low-frequency noise reduction capabilities.A complete active noise reduction system mainly consists of two parts,the upper active control software system and the hardware system.The software control system part largely determines the noise reduction performance of the system,which can be further subdivided into the underlying adaptive algorithm part and the corresponding control structure,which together determine the performance of the control system.Therefore,this article has carried out research from both aspects of adaptive algorithm and control structure.The adaptive algorithm is the lowest part of the control system.Improving the performance of the algorithm is conducive to improving the ability of active noise reduction.This paper studies the classic least mean square algorithm and the filtered least mean square algorithm.Combined with the characteristics of high dynamic signal processing faced by active noise reduction headphones,this paper proposes an improved RNLMS algorithm based on the Normal Least Mean Square algorithm.In this paper,a detailed algorithm analysis and computer simulation of the improved RNLMS algorithm are carried out.The computer simulation results show that the performance of the algorithm basically achieves the expected purpose.The principle of the active noise reduction headset is to cancel the initial noise by generating anti-phase noise through the speaker.The addition of the speaker system will inevitably introduce distortion of the frequency spectrum,which will complicate the secondary channel model,which is not conducive to the online identification of the primary channel in real-time active noise reduction.In order to improve this problem,this paper proposes a frequency equalization method based on inverse filtering;this method is applied to the feedforward and feedback compound active noise reduction earphone system,and a new active noise reduction control scheme is obtained.This method is also the core innovation of this research.For this reason,this paper gives a detailed system derivation process and related theoretical proofs,and the computer simulation results also fully prove the effectiveness of this method.In order to improve the noise reduction effect,the active noise reduction control scheme in this paper also compensates for the pollution caused by the secondary sound source speaker to the reference signal.In order to put this method into practical engineering application,this subject completed a set of active noise reduction earphone system based on TI's C6748 LCDK development board.Through the comparison of real-time active noise reduction experimental results,the system basically achieves the design purpose and fully demonstrates the superiority of the method proposed in the previous article.