i think the approach is wrong here.
as the codes are constantly testing ball1 size against ball2 size so even when there is no collision, the condition is constantly achieved.
i think i added the sound there so it will not give me the result of a sound when a collision occur but also during balls rubbing each other at the bottom.
should i use another approach like test of momentum transfer?
or maybe ball1 size against ball2 size && v1 or v2 > 0 ?
it is harder than i thought.