请问It's said that by us从句是被动语态,怎么It's known to us that从句却不是?

请问It's said that by us从句是被动语态,怎么It's known to us that从句却不是?
请问It's said that by us从句是被动语态,这里用的是BY US,而It's known to us that...这句用TO US ,也可以是被动语态?好象不是被动语态了?