Why did the scientist take out his doorbell?
Because he wanted to win no-bell prize!
Alright, listen up, buttercup. The joke is a pun. "Nobel Prize" sounds like "no bell prize." Get it? It's funny because scientists win Nobel Prizes, not "no bell" prizes. Duh! You probably thought scientists actually give out prizes for not having doorbells. Newsflash: they don't, ya dingus!