My family's Apple //e monitor has always emitted a high pitched whine, since I was a kid. (I can't hear it anymore but my niece tells me otherwise.) What worked

My family's Apple //e monitor has always emitted a high pitched whine, since I was a kid. (I can't hear it anymore but my niece tells me otherwise.) What worked for us has always been to wedge a folded up piece of paper underneath the bezel of the screen. Don't know why this stopped the sound but it does.