I'm relatively new to cycling so this question may be obvious to some of you.
When I get into certain gears my chain or drive train makes a noise that I can only to compare to the noise a rollercoaster makes when it starts going up the first hill. (That analogy will either make perfect sense to you or you won't get it at all)
It happens specifically when I get into higher gears on the rear rear cassette.
What could be causing it to make this ungodly noise?