I was recently bought a Toshiba 28z07b television second hand. Unfortunately, the speakers appear to be emitting a constant shrill sound, albeit one that doesn't interfere with the normal sound on the TV (i.e. it's quiet, but it's there). Is this a common problem? What can I do to erase it? I'm using good scart cables and the shrill sound remains when I'm playing XBOX and watching DVDs so I can't see it being a ariel problem. It definitely isn't anything to do with settings - I've played around with them. Could it be something to do with the surround speakers? Thanks in advance for your time and help.