Research Of The Least Distance Of Monopole Source In Active Noise Control

All kinds of noise will make us suffer the noise pollution, which are generated bycommercial activities, entertainments, services, promotional activities, householdappliances, industrial equipment operation during the process of production; buildersconstruct buildings regardless of the season and the night, the equipment on theconstruction site and the traffic on the road. Active noise control is a new kind oftechnology solving noise pollution in resent decades. It is able to supplement thedeficiencies of low-frequency noise control in traditional methods of noise control.The development of active noise control technology is analyzed and studied in thispaper. The methods of active noise control the seniors explored, whether on theimprovements in adaptive active noise control methods, or on the location optimizationof the anti-noise source and error sensor, are not related to the least distance between thetwo sources. The least distance is focused on and studied deeply in this paper. Firstly,the general acoustic knowledge that will be used in this paper is introduced briefly;secondly, monopole source is researched, and then sound power and sound intensityradial formulas are derived. The least distance is calculated to achieve the noisestandards base on the formulas. The conclusion is verified by physical experiment.Specific work and research results are as follows:①The sound field condition of the easiest source-monopole source is studied, byderiving the sound power formulas of monopole source, the least distances between thetwo sound sources to achieve the noise standards are calculated. When a monopoleanti-noise source is used to control a monopole noise source, it is improved that thesound power will decrease with the decrease in frequency of the two sound sources andthe decrease in the distance between the two sound sources. The lower the source’s ownintensity is, the better the result is.②The radial active sound intensity in the sound field of monopole noise sourceand monopole anti-source is derived. When the radial active sound intensity ofmonopole noise source is compared with the radial active sound intensity of the twomonopole noise sources, it comes out that for the active noise control of monopole noisesource; the noise reductions have a relationship with the frequency of the source and thedistance between the two sources. The lower the frequency is, the less the distance is,the better. The least distances between the two sources to achieve the noise standards are also calculated. The least distance has a relationship with the source frequency, thesource intensity and the distance from the source.③A simple experimental platform is built, the radial active sound intensity of anyspot in the space is focused on and the least distances between the two sources toachieve the standards are verified.