Abstract
Six patients with tinnitus resulting from head injuries were subjected to a variety of audiometric procedures in an attempt to determine the auditory characteristics of their tinnitus. For all patients but one, it was possible to match the tinnitus frequencies with sinusoidal test tones of specific frequencies. Presenting the matching test tone to the ear contralateral to that in which the tinnitus was heard resulted in a binaural fusion of the test tone and the tinnitus, causing a single sound image to be heard. By raising the intensity of the test tone, it was possible to lateralize the sound image entirely to the ear receiving the test tone, with the other ear silent. Whenever it was possible to fuse a patient's tinnitus with a contralateral test tone, it was also possible to create binaural beats between the tinnitus and the test tone by changing slightly the frequency of the test tone. One patient, W.P., when presented individually with contralateral test tones of the same apparent frequency as his two tinnitus, reported hearing neither his tinnitus nor the test tones. This observation confirms Wegel's report (7) that a tinnitus and a contralateral test tone may “cancel” each other. The only tinnitus that could not be matched by pure tones was the consequence of peripheral nerve damage rather than cortical injury. In general, tinnitus of central origin seems to have the same auditory characteristics as external sounds normally generated; by contrast, tinnitus of peripheral origin does not participate in the same forms of binaural interaction. The different characteristics of these two forms of tinnitus are the basis for the conflicting claims in the literature about the auditory characteristics of tinnitus.