耳鳴の遮蔽曲線と聽力との關係

　耳鳴の強さや耳鳴に含まれる周波數の測定にはいろいろの方法が考えられている。一側耳鳴の時にはloudness balanceを用いて，反對側の耳鳴と同じ大きさの音を示してもらえばよいが，實際には耳鳴は純音ではないので，純音とのバランスは仲々取り難い。又耳鳴と同じ樣な音を出すことも不可能に近い。もし耳鳴が純音と比較出來るような音であれば測定は可能であろう。他の方法は耳鳴をmaskする方法である。Kopetzkyの著書にもしも患者が耳鳴の音をmaskするに丁度必要な音或はその2倍の強さをきめることが出來れば大體の強さを知ることが出來るといつている。私はやはり耳鳴のmaskの方法を用いて耳鳴を検査し，その結果について種々検討を加えたのでここに報告し御批判を仰ぎ度いと思うのである。

OWADA and TSUBOI conducted a test by which they were enabled to eliminate symptoms of unilateral tinnitus with selected use of 14 different pure tones and, then, tried to estab-lish the relation between the hearing defect and elimination level, the level of tone at which the tinnitus is eliminated.

(1) Elimination level is shown to be loweredin correspondence to patient's hearing defects as they show in the audiometric chart, viz., the number of cycles that are shown in the hearing loss appears to coin-cida with that of tinnitus. The tinnitus of this nature when compared to normal ear in terms of decibels falls somewhere around 60-80db. in other words this type of tinnitus seems to be the result of disturbances occurring in the end organ of hearing or in the nerve itself and, consequently, it may be considered as non-vibrating. Twenty eight ears out of the 50 examined consisted of this type.

(2) The other type of tinnitus is characte-rized by accompaniment of slight loss of hearing that would be shown in the audiometric chart as a horizontal line.Elimination level reached by low tone would require the larger but as higher tones are approached that requirement becomes smaller; the frequency band which covers the tone of tinnitus would be narrow; the level be low; the hearing capacity be good. Such a type should be considered as belonging to the vibrating type of tinnitus and is encountered as a rule the result of middle ear disease.Six ears out of the 50 examined consisted of this type.