You heard him do this several times? In my limited experience with RI's I have found that wheezing or 'squeaking' can happen before you see any mucus/bubbles. its probably nothing but I would recommend letting him exercise for 15-20 min (do what you normally do, no need to turn the t.v off) then before you put him back make things completely quiet for 5 min and observe him, put him close to your ear again. The exercise will be good for him anyway if it is the early stages of RI but all that moving around will also encourage the 'squeaking' to happen again if it’s going to. Nothing to really worry about yet but keep an eye on him and see if any other signs of illness or RI show themselves.