An overall study of tinnitus was undertaken at our clinic using a newly developed tinnitus analyzer. This device has (1) a pure tone generator with a frequency range of 0.1 to 15 kHz, and (2) a noise generator with a range of 0.1 to 10 kHz which, with two pass filters, is capable of producing band noise of adjustable width and central frequency. This device was used to test such factors as tinnitus pitch and loudness, maskability, and residual inhibition (RI). The data were combined with in-. formation obtained from patient interviews and audiograms to prepare a comprehensive clinical profile of tinnitus, and were also applied to tinnitus masking therapy. The results of our investigation were as follows:
1) Most pitch frequencies were fou nd to be above 4,000 Hz.: 77% in patients with tonal tinnitus and 70% in those with band noise tinnitus. Only 32% of the t o nal tinnitus patients had tinnitus frequencies that would have been measurable by conventional fixed frequency audiometer.83% of the cases of band noise ti n nitus were found to have band widths of less than 1 octave, and 61 % had ba n d widths of less than 0.5 octave.
2) 91% of the tonal tinnitus cases and 84% of the band noise tinnitus cases showed loudness levels of under 10 dB.
3) A significant degree of RI was noted in cases of band noise tinnitus. RI was most often observed in patients with tinnitus band widths of under 0.5 octave. W ith the levels decreasing as the bands widths increased.
4) A greater incidence of head noise was reported by patients in which similar audiograms, tinnitus pitch and tinnitus loudness were found in both ears.
5) Approximately 50% of the patients reported an association between physical condition and subjective tinnitus levels. Muscle tension was the single most-mentio n ed factor.
6) Insomnia and fluctuations in tinnitus levels were found to be important factors in increased tinnitus discomfort.
7) Significantly higher incidences of band noise tinnitus were found in patients above 50, and in those with long term tinnitus, high level hearing losses. This is considered to be due to the greater incidence of cochlear dysfunctions in band n o ise tinnitus than in tonal tinnitus.
8) Various differences related to age, sex, and disease were found, and were summarized in tables 49 and 50.
9) Masking therapy was successful in 69% of the patients treated, on the basis of the criteria of maskability and patient comfort.
10) Masking proved effective for patients with fluctuating tinnitus levels when used at times of increased loudness, and for patients suffering from insomnia when used before sleep.

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