Mighty Mouse make annoying clicking noises when I rest my fingers on it

My Mighty Mouse (A1152) makes an annoying clicking noise when I rest my fingers on it. (While I am NOT actively clicking the buttons.) The noise is coming from the mouse's internal speaker. Occurs on both the right and left buttons. This is the second mouse that does the exact same thing. It is driving me bonkers! I'd like to know the root cause, but at this point just being able to turn off the sound would suffice.