my $9 wired earbuds from Sony also form a good ear seal by the way. No need to buy the $250 (!) thing from Apple. Unless you don't have a headphone jack.

I've used these to sleep to podcasts or quiet music at music festivals, and they block out the music from outside pretty well. This is because of the flexible rubber seal. My wireless earbuds are hard plastic all the way around and sit (securely) in my earlobes while my wired ones actually go inside my ear canal.