|MadSci Network: Physics|
Loudspeakers are optimized to only create acoustic waves of frequencies supplied by the electric current. All other waves they create are noise. The better they are optimized, the less noise they create. Not surprising, a power line, which is not optimized in such a way, creates more noise than frequency of the current (which is 50Hz in most parts of the world). I suppose that's the "white noise" you described. An occasional crackling sound could come from athmospheric discharges of static electricity, but this should only occur near very high voltage lines that are not usually near appartments (for safety reasons).
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