Tinnitus hum, but it can also arise as a subjective phenomenon from an increased awareness of blood flow in the ear. Rarely, pulsatile tinnitus may be a symptom of potentially life-threatening conditions such as carotid artery aneurysm or carotid artery dissection. Pulsatile tinnitus may also indicate vasculitis, or more specifically, giant cell arteritis. Pulsatile tinnitus may also be an indication of idiopathic intracranial hypertension. Pulsatile tinnitus can be a symptom of intracranial vascular abnormalities and should be evaluated for "irregular noises of blood flow" (bruits). The mechanisms of subjective tinnitus are often obscure. While it is not surprising that direct trauma
Tinnitus range and bandwidth in cases of narrow band noise tinnitus, loudness in dB above hearing threshold at the indicated frequency, mixing-point, and minimum masking level. In most cases, tinnitus pitch or frequency range is between 5 kHz and 10 kHz, and loudness between 5 and 15 dB above the hearing threshold. Another relevant parameter of tinnitus is residual inhibition, the temporary suppression or disappearance of tinnitus following a period of masking. The degree of residual inhibition may indicate how effective tinnitus maskers would be as a treatment modality. An assessment of hyperacusis, a frequent accompaniment of tinnitus, may also be