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 TRT is imputed to work by interfering with the neural activity causing the tinnitus at its source, in order to prevent it from spreading to other nervous systems such as the limbic and autonomic nervous systems. Clients are classified into 5 categories. These categories are numbered 0 to 4, and based on whether or not the patient has tinnitus with hearing loss, tinnitus with no hearing loss, tinnitus with hearing loss and hyperacusis, and tinnitus with hearing loss and hyperacusis for an extended amount of time. The first component of TRT, directive counseling, may change the way tinnitus is perceived.