Good Riddles

Question: Whoever makes me can hear me, but nobody else can.

What am I?

Question: I grow from trees and your home,
once I am grown I fall to my doom.

What am I?

Question: What can float but can't sink.

Question: What can you smell but not see. And can be deadly, too.

Question: A horse travels a certain distance each day. Strangely enough, two of its legs travel 30 miles each day and the other two legs travel nearly 31 miles. How is this situation possible?