2004 Hyundai Accent Weird car noise

I've noticed that you car is making a noise like a baseball card hitting the spokes of a bicycle. It is very soft, but it gets a little louder when I hit the gas. What does this noise mean, and about how much will it cost to fix it? Also, I try to do as much as I can on my own car, like change the oil and oil filter, air filter, spark plugs, battery, lights, and the front breaks. Is the answer to this type of problem something that I can fix myself, or is it something I should have fixed by a mechanic?