Tinnitus might be caused by inadequate circulation in the arteries that supply the inner ear with blood. It might be caused by atherosclerosis. Atherosclerosis is a condition in which the arteries are slightly narrowed because of plaques on the wall. The plaques contain mostly fat and calcium, which is why controlling fat levels in the blood is important. The condition can be worsened when the small muscles in the walls of the arteries strengthen themselves, thus causing additional narrowing of the arteries. Since the blood pressure is related to the diameter of the arteries, your father might experience more severe tinnitus when his blood pressure is raised. But, the blood pressure does not cause the tinnitus itself. It is just elevated from the same reasons that cause the tinnitus.