Trisha's rx8

Please someone help...I really don't know how to explain my issue. My car is making a weird sound when it idles. It is louder than normal, but more of a high pitch idle. It still gets good power but the idle is kinda off. When you are stopped it bogs a little but does not die. But I noticed a few days ago that it just sounds different. when you drive it, it sounds different than normal. Its almost like if you take two pieces of metal and barley hit them together as your passing over the other but really fast. I know I sound like I have no ideal what Im talking about. But thats the best way I can explain it. If you have questions to help I will be glad to answer them. I just need help.