So at the risk of showing myself to be a total bike nerd, I really have to ask this question:
When I coast my bike, the rear derallieur makes ticking sound (which is one of my favorite sounds ever)(see, I told you I could be a nerd), but my friend's bike doesn't. Why is that?
Depends on the make of the hub.
Shimano tend to be quiet whereas Campagnolo really tick. My Mavic can be heard 3 streets away. (only joking but it is very loud.)
Some Shimano hubs used to use a different set up and can't be heard at all.
[font=Trebuchet MS]Ride hard or ride home alone![/font]
It's the hub rather than the derallieur, and as cyclerUK said it depends on the hub. There's usually some form of "clicky noise," but tyre roar can drown it out if it's a quiet hub (pick the back end up and spin it).
If you really like loud hubs see if you can get hold of a Hope hub, particularly the Pro II (not sure if you can get them in the states, they're made in the UK). They're an MTB hub though, but they have one of the loudest clicks out there. They're also virtually indestructible and are so well made they rarely fail (almost everyone runs them for Downhill, and I've only ever heard of three fail, all were due to defects in manufacturing).
Just a note some sound the same no if it is a Freewheel or Freehub
. As long as you do not hear grinding sounds your ok hahaha.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!