Research On Local Active Noise Control System In Three Dimensional Space

Since the reform and opening up,China's economic take-off has promoted the vigorous development of all walks of life,which also aggravates the noise pollution.In the new era,people put forward higher requirements for living standard,and the ubiquitous noise has seriously affected people's health and quality of life,how to effectively control noise has become an urgent problem to be solved.Noise control technology is an important method to weaken and eliminate noise,because the traditional passive noise control technology can't deal with the problem of low frequency noise,active noise control technology has become an effective way to solve the low frequency noise.Currently,most active noise control products are aimed at special scenes such as pipes and earphones,while there are few noise reduction products for three-dimensional scenes with wide application.Based on the above problems,this paper starts from the principle of active noise control,through the analysis of typical structures and algorithms,for the local area of active noise control in three-dimensional space to do some related research.In order to ensure the stability of the control system,a method of off-line identification is used to estimate the relevant parameters of the secondary channel.Aiming at the steady-state error and convergence speed of the balance algorithm,the improved characteristics of the correlation variable step algorithm based on specific function are summarized by summarizing the three existing variable step algorithm.In addition,aiming at the problem that the error microphone cannot be placed close to the ear in some actual scenes,this paper combined with the virtual microphone technology to carry out relevant simulation tests for local active noise control in three-dimensional space,to verify whether the noise reduction can be achieved in the target area of human ear when the error microphone is a certain distance away from the human ear.In order to further study the active noise reduction in three-dimensional space,a two-channel local active noise control system based on DSP is designed and built.System based on achieve the optimal effect of noise reduction for the purpose,according to the active noise control system of acoustic signal acquisition,processing and output requirements,through comprehensive analysis and comparison,completed the microphone,speakers,audio codec,selection,and filter circuit,signal amplification circuit and power amplifier circuit design,in addition to the control system software design and implementation.To verify the actual noise reduction effect of this system on low and medium frequency noise,single and dual frequency noise control tests were designed in indoor threedimensional space.The acoustic signals at 3cm,5cm,8cm and 10 cm distance from the ear were collected by measuring instruments before and after noise reduction.The changes of sound pressure level before and after noise reduction were compared,and good noise reduction effect was achieved.In the single-frequency noise control test,the maximum measured noise reduction occurs at 5cm away from the ear,and the maximum value is13.95 d B at 850 Hz.In the dual-frequency noise control experiment,the maximum measured noise reduction occurs at the distance of 10 cm from the ear and the maximum value is20.40 d B at the frequency of 250&450Hz.The experiment shows that the dual channel local active control system designed in this paper can achieve obvious noise reduction effect in a certain local area,which provides a reference for the future three-dimensional active noise reduction and makes efforts to reduce the impact of noise on people's lives.