Final answer:
Tinnitus is the perception of sounds like ringing or hissing in the ears without an external source, often associated with conditions like sensorineural hearing loss and Ménière's disease, and may be treated with a cochlear implant in certain cases.
Step-by-step explanation:
The perception of ringing, hissing, or other sounds in the ears or head when no external sound is present is known as tinnitus. This condition can be a symptom of various underlying health issues, such as sensorineural hearing loss or Ménière's disease. Tinnitus can drastically affect a person's quality of life and is often associated with a degeneration of inner ear structures leading to hearing loss, vertigo, and increased pressure within the inner ear. Although there is no cure for tinnitus itself, treatments like cochlear implants may help those with sensorineural hearing loss by directly stimulating the auditory nerve to transmit information to the brain.