TV issues

Okay my mom has this 27 inch TV.. and its been going good for a while.. we have owned it for about a year.. but recently.. and at random times ( random to me) the tv has been emitting a VERY high pitched sound.. My mother doesnt hear it since she doesnt hear mucha nyway... but me and my friends always do.. Im just curious if there is a way to fix this?.. it happens ona ll the channels.. and only randomly.. sometimes it wont do it.. sometimes it does.. and its a o n and off thing.. like.. it goes.. Beeeppp.... beeeeeepp it isnt a beep though but I dunno how to describe this sound... its like a dog whistle or something.. but lower then that slightly.. Anyhow.. Iv checked the cable cable.. and the power.. could it be something interfereing with it some how?

Is it coming out of the speakers or the tv? Try muting the tv next time you hear it.