Funny noise/tone change

So my bike has been running great, no problems or things breaking. Recently tho, my bike has started to make a strange noise at 5K RPM, it does it for maybe the next 1K RPM then quits. The bike starts to rattle a bit and the engine tone changes noticably with a helmet on. Someone said something about a CCT or something, im not familiar with it. Any insight would be appreciated or any troubleshooting. Thanks.

well from the brief description it does sound like the cct. do a search for it, you will get hundreds of threads about if you shoudl replace it, how to replace it with pictures, what the alternatives are.....etc