Listing some of my ideas about that
- poor shielding of the rca cables (try to swap to thicker rca cables)
- power supply of rca to hdmi introduces noise (try a different power supply, easy if it uses something like a phone charger)
- ground loop / imbalance of grounds between rca to hdmi and PS2 or rca to hdmi and tv
- the rca to hdmi converter is not that good in quality and causes that buzzing noise ight want to read reviews from other people on the product, I'd say start with the lower ratings because some people just rate a product high 'as long as it works' even if not well)
- PS2 itself introduces the buzzing (regardless of the rca to hdmi) which could be an electrical issue like a capacitor going bad (this should be the easiest to test by plugging the PS2 directly to a tv with RCA)
But honestly a lot of things could be the source of the problem and from what I've seen on other people's PS2 to HDMI are using a PS2 to HDM like this or this
Also pretty sure this isn't the right sub to ask this question a sub like r/retrogaming could help you better