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 masker for hearing loss. Sound generators (masking devices) have received Class II approval from the FDA. However, they are considered to be “experimental, investigational, or unproven” therapies. There is one report of a bone conduction vibration masker that transmits a 60 Hz fundamental with adjustable harmonics up to 1000 Hz. A commercial device based on the phenomenon (Aurex3) was approved by the FDA. A new development in tinnitus management is the use of high audio (10 kHz-20 kHz) or ultrasonic (20-100 kHz) via bone conduction. A 2012 Cochrane Review stated the available studies do not show strong evidence of the efficacy