In order to investigate the influence of conductor surface’s contamination on the spectrum of the audible noise under positive DC voltage

an experiment platform was constructed to measure the audible noise of the single corona point in the laboratory. When the surface of the conductor was covered with salt

kaolin

and carbon

respectively

the spectra of the single corona point were measured and recorded under different positive DC voltage. The long-term spectrum measurements of different surface conditions were made under different voltage. The results reveal that the spectral components of the audible noise are obviously different with the increase of voltage applied on the clean conductor. The spectral components（>1 k Hz） of the polluted conductor are much higher than those of the clean conductor. The contamination adhering to the surface of conductor affects spectral components（>1 k Hz） much more obviously than low spectral components（<1 k Hz）. Since the speed of electrons and ions is fast in the strong electric field

and collision between neutral and charged particles can generate a momentum source

the momentum source can cause the perturbation of the air and produce acoustic source.