Ok, I've found what the buzzing sound is with my bass and it is coming from inside the neck. When I knock on the neck with my knuckle, I here the sound of something metal hitting wood. I'm assuming it's the truss rod, however it's been tightened. The bass plays fine and to the best of my knowledge the buzzing does not come through the amp. I realize my description of this problem is vague but does anyone have any advice on what I should do, if anything?