Hissing is one of several possible symptoms of tinnitus, according to WebMD. Other tinnitus symptoms include ringing, whistling, buzzing and roaring noises in the ears.
Tinnitus is a medical condition that affects the inner ear and is characterized by the presence of noise within the ear. Many health conditions can cause it or make an existing case of tinnitus worse. The most common cause of tinnitus is damage to delicate hairs in the inner ear that transmit sound waves via electrical signals through the auditory nerve and to the brain, explains Mayo Clinic. When the hairs become damaged, random electrical signals are sent to the brain, causing a noise. Other causes of tinnitus include hearing loss due to advancing age, exposure to loud noise, accumulation of earwax and otosclerosis.