This phenomenon is a symptom of the myofascial syndrome, that is, triggers points in the SCM muscle complex or the Masseter muscle. Contracting, or otherwise pressuring any muscle innervated by the Mandibular branch of the Trigeminal nerve can either interrupt, or increase the volume of the tinnitus, only for as long as the muscle or muscles are contracted. The myofascial syndrome (reference pain), is often mistaken for the pain of TMJ arthritis.
