Buzzing sound

I'm not too concerned , but... I have noticed a buzzing sound down by my left foot (crankcase?) I'm not sure if it was there since it was new since I only hear it when my legs are a bit away from the tank and last fall I was probably death gripping the tank with my legs. The sound is quite high pitched (rattlesnake) and goes away when I let off the throttle. Is this just normal chain noise?