I have never had it. I don't think it is medically related to BP. It is related to being exposed to loud sounds or music. It damages the hairs which pick up sounds, and then they try and make noise to replace the sound they cannot hear.

http://www.emedicinehealth.com/tinnitus/page2_em.htm

My husband has it quite badly, because of working with power tools. He is not bipolar.