Most of the causes of tinnitus alter neurological activity within the auditory cortex, the portion of the brain responsible for hearing. The transmission of sound is interrupted, so some of the neural circuits fail to receive signals. Instead of causing hearing loss, as you might expect due to the lack of stimulation, the neural circuits begin chattering. First, they chatter alone. Then, they become hyperactive and synchronous. When we experience this deviation, our brains attempt to compensate for the change by interpreting the neurological activity as sound. This can resemble ringing, buzzing, hissing, whistling, or roaring, amongst a variety of other noises.

Prolonged exposure to loud sounds is the most common cause of tinnitus. Up to 90% of people with tinnitus have some level of noise-induced hearing loss. The noise causes permanent damage to the sound-sensitive cells of the cochlea, a spiral-shaped organ in the inner ear. Carpenters, pilots, rock musicians, street-repair workers, and landscapers are among those whose jobs put them at risk, as are people who work with chain saws, guns, or other loud devices or who repeatedly listen to loud music. A single exposure to a sudden extremely loud noise can also cause tinnitus.
The exact biological process by which hearing loss is associated with tinnitus is still being investigated by researchers. However, we do know that the loss of certain sound frequencies leads to specific changes in how the brain processes sound. In short, as the brain receives less external stimuli around a specific frequency, it begins to adapt and change. Tinnitus may be the brain’s way of filling in the missing sound frequencies it no longer receives from the auditory system.

Pulsatile tinnitus is generally caused by abnormalities or disorders affecting the blood vessels (vascular disorders), especially the blood vessels near or around the ears. Such abnormalities or disorders can cause a change in the blood flow through the affected blood vessels. The blood vessels could be weakened from damage caused by hardening of the arteries (atherosclerosis). For example, abnormalities affecting the carotid artery, the main artery serving the brain, can be associated with pulsatile tinnitus. A rare cause of pulsatile tinnitus is a disorder known as fibromuscular dysplasia (FMD), a condition characterized by abnormal development of the arterial wall. When the carotid artery is affected by FMD, pulsatile tinnitus can develop.


In the advance online edition of Nature on January 12, 2011, the researchers reported that the number of neurons tuned to the high frequency had jumped by 79% compared to control rats. The scientist then tested 2 different tones in a second group of rats but stimulated the vagus nerve only for the higher one. The neurons tuned to the higher tone increased by 70%, while those tuned to the lower one decreased in number. This showed that the tone alone wasn’t enough to initiate the change; it had to be accompanied by VNS.

When a medication is ototoxic, it has a toxic effect on the ear or its nerve supply. In damaging the ear, these drugs can cause side effects like tinnitus, hearing loss, or a balance disorder. Depending on the medication and dosage, the effects of ototoxic medications can be temporary or permanent. More than 200 prescription and over-the-counter medicines are known to be ototoxic, including the following:
Tinnitus is a symptom, not a disease. Most cases are due to damage to the microscopic endings of the sensory nerve in the inner ear, commonly from exposure to loud noise (as from amplified music or gunfire). Other causes include allergy, high or low blood pressure, a tumor, diabetes, thyroid dysfunction, and head or neck injury. In addition, some drugs, including aspirin and other anti-inflammatories, antibiotics, sedatives, and antidepressants can also cause tinnitus. If so, changing drugs or lowering the dosage usually helps.
Why is tinnitus so disruptive to sleep? Often, it’s because tinnitus sounds become more apparent at night, in a quiet bedroom. The noises of daily life can help minimize the aggravation and disruptiveness of tinnitus sounds. But if your bedroom is too quiet, you may perceive those sounds more strongly when you try to fall asleep—and not be able to drift off easily.
Tinnitus is not a disease but a symptom that can result from a number of underlying causes.[2] One of the most common causes is noise-induced hearing loss.[2] Other causes include ear infections, disease of the heart or blood vessels, Ménière's disease, brain tumors, emotional stress, exposure to certain medications, a previous head injury, and earwax.[2][4] It is more common in those with depression.[3]
The patients were assessed at the start of the study for their hearing ability and the severity of their tinnitus. The researchers assessed the degree of severity using established questionnaires, which looked at health-related quality of life, the psychological distress associated with tinnitus and how far it impaired their functioning. Using this information, researchers divided participants into four groups ranked on the severity of their condition.
An assessment of hyperacusis, a frequent accompaniment of tinnitus,[56] may also be made.[57] The measured parameter is Loudness Discomfort Level (LDL) in dB, the subjective level of acute discomfort at specified frequencies over the frequency range of hearing. This defines a dynamic range between the hearing threshold at that frequency and the loudnes discomfort level. A compressed dynamic range over a particular frequency range is associated with subjectve hyperacusis. Normal hearing threshold is generally defined as 0–20 decibels (dB). Normal loudness discomfort levels are 85–90+ dB, with some authorities citing 100 dB. A dynamic range of 55 dB or less is indicative of hyperacusis.[58][59]
Microvascular compression may sometimes cause tinnitus. According to Levine (2006) the quality is similar to a "typewriter", and it is fully suppressed by carbamazepine. It seems to us that response to carbamazepine is not a reliable indicator of microvascular compression as this drug stabilizes nerves and lowers serum sodium. Nevertheless, this quality of tinnitus probably justifies a trial of oxcarbamazine (a less toxic version of carbamazepine).
It can often be very helpful to talk to someone who understands how you are feeling, who can reassure you about any anxieties you may have, and answer your questions. We can provide details of self-help groups and contacts in the UK, and we also run a helpline on 0800 018 0527. Most of the people who run groups or are contacts have tinnitus themselves and have been helping people with the condition for a long time. Even if you don't want to take part in group activities, it can be a comfort to know there is someone you can contact.
Prolonged exposure to loud sounds is the most common cause of tinnitus. Up to 90% of people with tinnitus have some level of noise-induced hearing loss. The noise causes permanent damage to the sound-sensitive cells of the cochlea, a spiral-shaped organ in the inner ear. Carpenters, pilots, rock musicians, street-repair workers, and landscapers are among those whose jobs put them at risk, as are people who work with chain saws, guns, or other loud devices or who repeatedly listen to loud music. A single exposure to a sudden extremely loud noise can also cause tinnitus.
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