We discussed that, a video of the wire supplied at http://www.cnet.com/forums/discussions/static-sound-coming-from-tv-when-volume-is-off-help/
Easy fix if you fix your own stuff.
I own the Vizio SV420M 42 inch television. I have had it for about 4 years. It has been a great tv. About a month ago, when I turn on the tv, on random occasions I will hear a static / hissing noise coming from the tv speakers. I turned the volume down on the tv all the way to 0, and the static / hissing is still heard. It is loud. It only stops if I turn the tv off and on again. The static sound will then go away, until I turn the tv off for a while and turn it back on. I have checked all cables, took them out put them back in and nothing helps. I have the Sony HT260H sound bar hooked up to it using an optical cable. I also have a PS4, direct tv receiver, and x box 360 hooked up using HDMI cables. I have been searching online for a month now, with no help. I have contacted Vizio support, and all they could tell me is it's no longer under warranty and they give me numbers to tv shops. I don't want to take it to a shop if it's an easy fix. Please help!!! Here are some more observations I have made. The hissing sound happens no matter if the tv speakers are turned on or off. The hissing sound is coming through the tv speakers not the sound bar. When I pan the balance back to right and left speakers, the hissing sound doesn't change. When I turn the volume up on the tv to about 45 the hissing starts to pop and it stops.