Diagnosis
The basis of quantitatively measuring tinnitus relies on the brain’s tendency to select out only the loudest sounds heard. Based on this tendency, the amplitude of a patient's tinnitus can be measured by playing sample sounds of known amplitude and asking the patient which she or he hears. The volume of the tinnitus will always be equal to or less than that of the sample noises heard by the patient. This method works very well to gauge objective tinnitus (see above.) For example: if a patient has a pulsatile paraganglioma in his ear, he will not be able to hear the blood flow through the tumor when the sample noise is 5 decibels louder than the noise produced by the blood. As sound amplitude is gradually decreased, the tinnitus will become audible, and the level at which it does so provides an estimate of the amplitude of the objective tinnitus.
Objective tinnitus, however, is quite uncommon. Often patients with pulsatile tumors will report other coexistent sounds, distinct from the pulsatile noise, that will persist even after their tumor has been removed. This is generally subjective tinnitus, which, unlike the objective form, cannot be tested by comparative methods.
If the attention of a subject is focused on a sample noise, she can often detect it at levels below 5 decibels, which would indicate her tinnitus would be almost impossible to hear. Conversely, if the same test subject is told to focus only on the tinnitus, she will report hearing the sound even when test noises exceed 70 decibels, making the tinnitus louder than a ringing phone. This quantification method suggests subjective tinnitus relates only to what the patient is attempting to hear. Whilst it is tempting to assume patients actively complaining about tinnitus have simply become obsessed with the noise, this is only partially true. The noises are often present in both quiet and noisy environments, and can become quite intrusive to their daily lives. The problem is involuntary; generally, complaining patients simply cannot override or ignore their tinnitus.
Subjective tinnitus may not always be correlated with ear malfunction or hearing loss. Even people with near-perfect hearing may still complain of it.
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