Recently I've noticed that I have a 'new' type of tinnitus. It is an extremely low pitched sound. Volume is pretty low but audible at night. It sounds like there is a machine or helicopter making noise, but very far away. At the same time, I'm sure it comes from within my head. Really in the middle. It does seem to vary slightly on the rythm of my heart beat. I think I have it for a couple of months now. I already have a (not very loud) constant high pitched tinnitus as wel as a pulsatile humming tinnitus. What could this new tinnitus be caused by? Are low pitched tinnitus more like to be caused by something serious, like restricted blood flow or tumors or anything? Anyone any idea or experience? Thanks!