Intensity Difference LimenとRecruitment

抄録

Author designed a new procedure to assess intensity difference limen (I. D. L.) in normal person and in patient with hearing loss, -utilizing the apparatus for the SISI of a commercialized audiometer and adopting psychophysically the up-and-down method.
I. D. L. to low tones (250Hz and 1000Hz) in normal ears could be expressed by one hyperbolic function of sensation level, from 5dB to 80dB re S.L. At 4000Hz, also at 8000Hz, two hyperbolic functions were needed for each range above and below about 40dB re S.L.
I. D. L.'s in patients with sensori-neural deafness, being measured by the same procedure and compared by the sound pressure level of the sustained standard tone, were equal to the normal I. D. L.'s above a certain level, just as the loudness of impaired ear becomes equal to that of normal ear in Fowler's method. This intensity level, above which I. D. L.'s of deaf ears proved to be normal, was named as the recruiting level.
The intensity range between the recruiting level and the elevated threshold level, which was named as the recruiting range, was supposed to be essential for the deaf ear to percept the intensity change. It was deduced that even in normal ear a critical intensity range, something like the recruiting range of pathological ears, should be present. I. D. L.'s in ears with conduction-loss could not be compared with that of the normal ear in the above-mentioned manner, because the sound energy, before arriving at the sensory part, was converted in various ways by the pathological conditions.