We are twins
We are the gateway of silence
We enrich your world, but you can live without us.
We are your friends, but sometimes we can be loud when you don't want us to be.
Sometimes we annoy you, but you will never want to lose us.
Who or what are we?
Sometimes we can be blocked, but that is only temporary.
Another new hint:
We are usually dry but sometimes we flood.
3rd new hint (this hint almost gives it away, but I can't resist):
Some children think we provide food, but we don't.
I will give a new hint for every wrong answer.