Tinnitus is the perception of sound within the ears or head when no external source is present. It is a common symptom of an underlying issue, often related to the auditory system, rather than a disease itself. The “sound” is a highly variable experience, ranging from a mild distraction to a debilitating noise that interferes with daily life.
The Auditory Experience of Tinnitus
The most frequently described sound is a high-pitched, steady ringing tone, sometimes analogized to a tea kettle or a dial tone. This high-frequency sound is often closely linked to hearing loss, which is the most common predisposing factor for tinnitus. However, the auditory experience extends far beyond simple ringing and is deeply personal to each individual.
Many people report a persistent hissing sound, similar to escaping air or the static from an untuned radio station. Others describe a low-frequency buzzing, which can resemble the distant hum of an electrical transformer or the sound of a swarm of insects. The pitch of the sound can vary dramatically, from a deep, low roar, like ocean waves or distant machinery, to a sharp, intense whistle.
The volume of the perceived sound is also highly inconsistent, ranging from a faint background presence only noticeable in quiet environments to a loud, intrusive noise that seems to mask all external sounds. Some individuals experience intermittent sounds, such as a rapid clicking or crackling, which may be tied to muscle movements in the middle ear. The fluctuating nature of these sounds makes the auditory experience complex and unpredictable.
Classifying Tinnitus Sounds
Tinnitus is generally classified into two major categories based on who can hear the sound. The vast majority of cases, representing over 99% of all reported instances, are classified as subjective tinnitus. This means the sound is a phantom perception, heard only by the patient, and results from activity within the neural pathways of the auditory system.
A rare form of the condition is objective tinnitus, which is the only type a physician might be able to detect during an examination. Objective tinnitus is caused by an actual physical process that generates a sound, such as muscle spasms in the middle ear or alterations in blood flow near the ear structures. The sound is an internal body noise that is loud enough to be transmitted to the ear canal.
A specific subcategory is pulsatile tinnitus, which is rhythmic and typically described as a whooshing, swooshing, or thumping that pulses in time with the person’s heartbeat. While often considered objective, it can sometimes be subjective. Pulsatile tinnitus often indicates a vascular issue, such as turbulent blood flow through irregular blood vessels near the ear. Because conditions like high blood pressure or atherosclerosis can cause this rhythmic noise, prompt medical evaluation is necessary.
Understanding the Internal Source of the Sound
The perception of tinnitus, particularly the common subjective type, is not usually caused by a problem in the ear itself, but rather by the brain’s reaction to a lack of sensory input. Damage to the delicate hair cells in the cochlea, often due to acoustic trauma from loud noise exposure or age-related decline, reduces the signals sent along the auditory nerve to the brain. This lack of expected input is known as deafferentation.
In response to this reduced signal, the central auditory system, including the auditory cortex in the brain, attempts to compensate by increasing its sensitivity or gain. This compensatory mechanism leads to neural hyperactivity, where certain groups of neurons begin firing spontaneously and synchronously.
This phantom sound is the brain creating noise to fill the silence left by the damaged peripheral ear structures. Common triggers for the initial damage include exposure to loud sounds, age-related hearing decline, and certain ototoxic medications.
While most tinnitus is benign, certain symptoms require professional evaluation. These include sudden onset, tinnitus affecting only one ear, or any pulsatile sound. Medical advice is also important if the sound is accompanied by sudden hearing loss, dizziness, or facial weakness.