聽覚による方向識別に関する研究（其の一）（周波数・強さ）

吾人の聴覚で前正中線と感じるのは一定の拡りを指すのであるが,この範囲は略々解剖学的前正中線附近に正しく局在されている.この範囲は同一周波数の音源では拡りが一定であり,周波数の変化により範囲の大さを異にする.こゝに着眼して周波数による前正中線附近の方向感度を観察し,之が中周波域に於て最も良く,低周波稍々悪く,高周波域に於ては極めて悪い結果を見た.音源の強さに関しては,最小可聴閾より5～15d. b.上昇域に於て略定位可能であるが,多数の人員に対して完全を期する為には最小可聴閾より30d. b.以上の強さを要する事を見た.

A bone conduction receiver connected to the audiometer is used as the source of the sound. The examinee used a rubber tube binaurals, which was 2 meters in length, and was able to hear the source of the sound placed 2 cm right or left from the middle of the receiving tube alternatively. When it was 2 cm to the right, the examinee answered "right", and when 2 cm to the left, the answer was "left" Frequencies and intensities of the source of sound varied. The sound localizes best between 128--1024 v. d., and becomes worse on the lower or higher frequencies. The intensity between 5--15 d. b. over the threshold is at least needed to locate the source of sound. For accurate hearing an intensity greater than 30 d. b. is desirable.