Tinnitus is the perception of sound when no corresponding external auditory stimulus is present. This internal sensory experience is generated within the auditory pathway or the brain itself. It is a highly common occurrence, though the nature of this internal sound is extremely variable among individuals.
The Primary Auditory Manifestations
The most frequent description of tinnitus is a pure, high-frequency ringing sound, often likened to a bell or a sustained pure tone. This manifestation is so prevalent that the condition’s common name refers to it.
Many individuals describe the sound as a persistent hissing, comparable to static noise from an untuned radio or escaping steam. This noise is typically perceived as a broadband sound, covering a wide range of frequencies rather than a single tone.
Another common category includes buzzing or humming sounds. These are generally lower in frequency and often described as mechanical or like a distant electrical transformer, sometimes having a continuous, droning quality.
Less common are clicking or pulsating sounds. Clicking may be rapid and erratic, occasionally indicating muscular spasms in the middle ear. Pulsating sounds are typically rhythmic, perceived as a whooshing or throbbing that aligns with the person’s heartbeat.
The Perception of Pitch and Volume
The subjective pitch of the perceived sound varies widely, ranging from a low-frequency roar to a high-frequency squeal. Higher-frequency sounds are frequently reported by people with noise-induced hearing loss, often corresponding to the frequency range where damage is present. Conversely, low-frequency sounds may be more common in people with certain conductive hearing issues or inner ear disorders.
The volume of the phantom sound is also highly subjective, spanning from barely perceptible to intensely loud. For many, the sound is only noticeable in quiet environments, such as when trying to sleep. For others, it can be loud enough to interfere with daily concentration or the ability to hear external conversations.
Scientific measurements often show the internal sound is matched by a low sensation level, typically 6 to 20 decibels (dB) above the hearing threshold. However, this low measurement does not mean the sound is perceived as soft. Due to loudness recruitment, especially with hearing impairment, a sound at a low sensation level can be perceived as significantly louder.
Location and Timing of Sounds
The spatial origin of the perceived sound can be unilateral (affecting one ear) or bilateral (present in both ears simultaneously). In some cases, the sound is not localized to the ears but is perceived as a centralized noise originating from within the head. The location can occasionally shift or change over time.
The experience can be continuous (present without interruption) or intermittent and episodic. Intermittent tinnitus may occur temporarily, often in response to specific triggers like increased stress, fatigue, or loud noise exposure. The sound may also fluctuate in intensity throughout the day or night.