Tinnitus activity in the limbic system and autonomic nervous system, thus increasing tinnitus awareness and annoyance. There are two types of tinnitus: "subjective tinnitus" and "objective tinnitus". Tinnitus is usually subjective, meaning that there is no sound detectable by other means. Subjective tinnitus has also been called "tinnitus aurium", "non-auditory" or "non-vibratory" tinnitus. In very rare cases tinnitus can be heard by someone else using a stethoscope, and in less rare – but still uncommon – cases it can be measured as a spontaneous otoacoustic emission (SOAE) in the ear canal. In such cases it is objective tinnitus, also called "pseudo-tinnitus"
Tinnitus retraining therapy with tinnitus have a comorbid psychological injury or illness (e.g., post-traumatic stress disorder, depression, anxiety, obsessive compulsive disorder, stress, dysfunction of the temporomandibular joint, etc.) that can exacerbate the tinnitus. It has been proposed that tinnitus is caused by mechanisms that generate abnormal neural activity, specifically one mechanism called discordant damage (dysfunction) of outer and inner hair cells of the cochlea. The psychological basis for TRT stems from the fact that the brain exhibits a high level of plasticity. In turn, this allows it to adjust to any sensory signals as long as they do not lead to negative effects.