What does

For years I have been reading user comments on this forum about dirty power and how it can be corrected or minimized with power conditioners and dedicated circuits. I have recently been plagued by an annoying hissing sound that appears in only one of my two speakers at a given time and sounds an awful lot like radio station static. Sometimes it in the right channel, sometimes it is in the left channel. It is not there all of the time, but shows up only occasionally. The sound seems to last anywhere from a few minutes to the better part of an hour or so before it simply disappears. Dirty power? Time for some dedicated circuits?