Because, in most cases, the exact cause of tinnitus is not known, diagnosis typically begins with a visit to an ear specialist known as an otologist or otolaryngologist. A thorough clinical evaluation, including a complete patient history and medication regimen, helps the doctor to determine if tinnitus is present and what may be the cause of the condition. Specialized tests are performed to diagnose tinnitus. Some of these tests measure the specific features of the tinnitus itself. These tests may include:
- Evoked response audiometry
- Tinnitus pitch match
- Tinnitus loudness match
- Maskability of tinnitus
- Residual inhibition
X-rays films of the head are sometimes ordered to determine if any structural problems are present in the ear that may cause tinnitus. More high tech tests like an MRI or a CT scan may be ordered.
An audiogram, also known as a hearing acuity test, is a test that produces a chart measuring a person's ability to hear sound and recognize various speech sounds. Because some hearing loss is usually associated with tinnitus, an audiogram is helpful with the diagnosis.
Evoked response audiometry is usually done for people who have tinnitus in one ear only. This test consists of painless computerized inner ear recordings that are similar in principle to the computer "fault-finding" checks that car garages use on computerized car engines.
This test is based on the fact that ordinary physical tones have a pitch that corresponds to the frequency of each tone. Frequency refers to the number of cycles a sound wave completes in one second. Some sound waves have very high frequencies, while others are very low. For example, household electricity is at 60 cycles per second (60 Hertz or 60 Hz).
- To identify the "pitch" of tinnitus, the person selects from a group of external tones or noises. The selected tones are those that most closely match their tinnitus.
- A good way to imagine the value of this test is to consider that the highest tone produced on a grand piano cycles at slightly over 4,000 Hz. According to recent data, 74 percent of people with tinnitus have a "pitch match" for their tinnitus at 3,500 Hz or higher. Tones in this range typically have an unpleasant, screeching quality.
The loudness of tinnitus is evaluated by adjusting the loudness of an external tone that most closely matches the sounds of the tinnitus. The test proceeds until the external tones are as loud as the tinnitus.
- Using this technique, the actual loudness of the tinnitus is measured. Typically, it is more of a whisper than a shout, between 4 and 7 decibels (or dB) above the threshold of hearing. This finding presents somewhat of a puzzle. Frequently, people describe their tinnitus as being "very loud," when in fact the measurable "loudness" is in the very low range of 4 to 7 dB.
- Because of the difference between actual loudness and perceived loudness, another test known as the Visual Analog Scale is administered.
- This scale is a horizontal line marked off in equal units (like a ruler), from zero to 10. A rating of zero means "no tinnitus" while a 10 means the "loudest tinnitus one can imagine."
- The person selects the number on the scale that best represents the loudness of their tinnitus. Using this scale, 70 percent of people tested chose a value of six or above. This seems to confirm that tinnitus is perceived as a loud noise.
The maskability of tinnitus measures the degree to which tinnitus may be covered up or "masked" by other external sounds.
- This test uses a band of noise for the external or
maskingsound. In scientific terms, this noise band extends from 2,000 Hz through 12,000 Hz and is painlessly applied by using earphones on the affected ear.
- During this test, the masking sound is increased gradually until its presence is detected. Then the pitch of the sound is further increased until the person can no longer hear the tinnitus in that ear. The minimum masking level (MML) is expressed in dBsensation level (SL). In most people, the MML is 8 dB SL or less. It is rare for the MML to go above 22 dB SL.
This test records the amount of time that the noise in the ear is reduced or eliminated following a period of masking. The test is conducted by masking the tinnitus at a minimum masking level plus 10 dB for 60 seconds. After this period of masking, the length of time the tinnitus has improved, if at all, is determined.
- In this test, 85 percent of those tested displayed either complete or partial residual inhibition (that is,improvement in the noise heard in the ear). The average duration was 65 seconds.
- A test period of 60 seconds, producing a residual inhibition that lasts 65 seconds, does not mean that a one-hour test would produce one hour of residual inhibition.
- Making the masking sound louder does not increase the length of time or the level of the residual inhibition. However, some people who use masking extensively over long periods of time find that residual inhibition may be extensive, lasting hours or even longer.