固定周波数描記による聴力閾値の観察

　Békèsy型Audiometer即ち連続周波数自記Audiometerを使用し，周波数を固定して聴力閾値の時間的変動経過を記録する試みは，すでにLierle and Reger^1）2） Kos^3），立木^4）5）6）等によつてなされ，種々興味ある所見が報告されている。本法による閾値音の持続聴取に際しておこる閾値変動は，一般にtemporary threshold shift（TTS）或はauditory threshold fatigueと慣称されている。

　私も感音系難聴の細別診断の立場から，さきに志井田^7）と共に固定周波数描記を行い，感音系難聴耳について閾値変動の見られる場合と，然らざる場合のあることを報告したが，以来症例を重ねてTTSと障碍部位との関係を追求した結果，興味ある成績を得たのでその概要を報告する。

Taguchi, by means of Beltesy audiometer, makes clinical studies on the question of temporary threshold shift. The results are as follow:

1) Shifts in threshold sensitivity are noted to be very slight or none at all in the ears whose hearing is normal or involved with conductive or inner ear deafness. However, a moderate threshold shift is found in deaf-ness due to acoustic trauma.

2) Threshold shifts are noted to be extre-mely rapid or irregular in character in cases that are involved with retrolabyrinthine disorders.

3) Threshold shifts large and rapid are demonstrated in certain brain tumors without hearing impairments which is to say that, such cases belonging categorically to that of latent hearing disorders that can not be revealed by routine method of audiometry yet, the loss of hearing in these cases may be found by present method.