I've noticed recently that there is a buzzing sound that seems like it's coming from my mouthpiece under my front teeth. I've tried swabbing out the mouthpiece and using a new reed, neither have helped. It goes away slightly when I play louder, but doesn't disappear. What could it be? I've only been playing for 4 years, I'm by no means an expert. So maybe one of you could help me find out what's wrong?