Research On Sound Field Control Technology In Active Noise Reduction System

With the rapid development of industrial technology,indoor noise has an increasingly large impact on people’s lives and work.Therefore,people have higher requirements for indoor noise reduction.Compared to passive noise reduction,active noise reduction technology can reduce more widely frequency noise.However,when active noise reduction technology is applied indoors,it faces challenges such as the grating effect of the speaker array and the changing angle of noise incidence over time,which affects noise reduction effectiveness.Therefore,this thesis mainly studies the relationship between the speaker array and the sound field morphology,and proposes the use of array beam steering technology to improve the effectiveness of indoor active noise reduction.Firstly,this thesis establishes one-dimensional and two-dimensional models for the speaker and derives the directivity functions for the linear array and the planar array.By analyzing the impact of factors such as element length,number of elements,and array pitch on sound field morphology using the control variable method,and implementing array beam steering control using the time delay method.The results show that array beam steering changes the critical conditions for grating occurrence.Then,the COMSOL software is used to establish an indoor sound field model,and simulations of direct and standing wave field control using the speaker array are conducted.The results show that planar array control is better than linear array control,improving control effectiveness by about 20 d B when the noise frequency is 200 Hz.The use of array beam steering technology can effectively reduce obliquely incident indoor noise,and using a speaker planar array and beam steering technology can achieve reduction of noise in the entire indoor space.Finally,this thesis designs a hardware system platform and conducts directional testing of the speaker and active noise control experiments.In the active noise control experiment,beam steering control is combined with normalized Fx LMS filtering.The experimental results show that the directionality of the speaker agrees with the simulation results,and the speaker array beam steering technology can effectively improve control effectiveness when noise is obliquely incident.