Since about a month ago my speakers have randomly (when not listening to any audio) been making a soft white static noise for about a second, and then it stops. This has happened on two computers in my house, the speakers on one of them being relatively high end, and the others are definitely not bad. I don't have any cell phones around the computers and TVs are a good distance. I've tried lowering all volumes, including wave etc. under volume control panel. Any ideas?