Abstract
Using the magnifying otoscope, the acoustic reflex of tympanic muscles was investigated by the retraction-grade measuring of the tympanic membrane when the various tone stimuli were given to the human ear. The following results were obtained.
1). The change of the grade of retraction of the tympanic membrane was observed when both ears or each ear had been, simultaneously or successively, stimulated respectively by a tone of definite intensity and of various frequencies for two minutes.
a). In the stimulation of both ears the retraction was markedly in the range from 256 to 2048 cps, in which the response to 1024 cps was most remarkable, and was very slight or showed no change in the tone below 128 cps or above 4096 cps.
b). The frequency characteristic, in the stimulation of opposite ear, was similar to that in the stimulation of both sides, however, the degree of retraction was less than the latter.
2). The change of the retraction-grade was measured by increasing the intensity of the stimulating tone. The minimum phones in respective frequencies raising retraction of the tympanic membrane were as follows.
64 cps80,128 cps74,256 cps70,
512 cps72, 1024 cps67, 2048 cps72,
4096 cps74, 8192 cps73-83.
