Both the clinical study on the measuring method by use of a measuring apparatus of speech articulation, of which the tone source was put in tape-type magnetic recorder and speech is reproduced by a speaker, and the results of examination in the clinical use of this apparatus have been audiologically discussed.
NY-A Audiometer was used for measuring the pure tone hearing.
1) In examination, thirty words of Auditorially Ballanced (A.B.-) List (Kawata) were used.
2) For getting the maximum percentage of articulation and the types of the articulation curve, the descending measurement in which the intensity of speech decreases gradually from the intense stimulus to the weak, and the ascending one, from faint speech to strong, were comparatively examined in the intact ears and in various cases who were hard of hearing. From the results, the latter may be more useful than the former.
3) The articulation curves of speech were classified in five types from their characteristics, and the hearing curves to pure tone were arranged in nine types by the classification of Prof. Kawata, the interrelation between both being discussed simultaneously.
4) The articulation curve in conductive deafness shows a smooth inclining curve parallel with the curve of the normal ear: however, the discrimination loss is generally very slight. Most of the hearing curves to pure tone can be divided into two types, the horizontal type and the abrupt type, but there is no oblique declining type.
5) The greater cases of articulation curves in perceptive deafness show the two types of horizontal and descending after reaching at certain critical level on the ascending curve, the discrimination loss is in general large.
The order in the rate of the hearing curves to pure tones is the abrupt type, then the oblique descending one, and finally the horizontal one, but there is no oblique ascending type.
6) There is little difference in the articulation curve types and in the speech hearing loss between conductive deafness and perceptive or between perceptive deaf ears.
In conductive deafness, if the hearing curves to pure tone are similar the remarkable difference in type of curve and also in the speech hearing loss can not be observed.
7) For estimating the loss value of pure tone hearing which is considered as the loss value of speech hearing, the method containing the air-conductive hearing loss in 4000 cps and that without this loss were used. In the comparison of the value by these two methods with the value of hearing loss for speech, the method without addition of hearing loss in 4000 cps tends to decrease the value. But the significant difference in the hearing loss for speech or pure tone loss can not be observed between these two estimation methods.
8) In the observation of the sudden descending type in perceptive deafness, the effect of the decrease of hearing power on the articulation is remarkable at the lower frequency in comparison with that at the higher frequency of speech area (500-4000 cps).
9) The similarity in the hearing loss for speech and pure tone loss is less in perceptive deafness t1-2n in conductive. In general the speech hearing loss is larger, especially marked in the unknown -caused nerve deafness. On the contrary, the lower frequency zone of the speech area is kept at relatively high level in acoastic- traumatic deafness, and the hearing loss for speech remains relatively slight.

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An experimental study on the acoustic reflex of tympanic muscles was carried out from various points of view.
First, the observation on the effect of an acoustic tympanic muscle reflex indicated by cochlear electrical response resulted in the following facts.
a) The change of amplitude of microphonic response of the animal, in which the tensor tympani was cut, to the definite noise is larger than that without cutting, and especially at the lower frequency the decrease of amplitude of microphonic potential is observed.
b) When the stapedius is cut, the change of amplitude of microphonics is larger than that of tensor-tympani-cut group at the lower frequency.
c) With exposure to the same noise, the decrease of micorophonic potential is more remarkable in the group where both tendons of the tensor tympani and of the stapedius are cut than in the group of a single cut.
d) In the general application of anticonvulsant, the microphonic potential increases temporarily and markedly, however, it gradually decreases with time.
e) Immediately after the injection of curare preparation into the unilateral carotis, the microphonic potential in the injected side, as well as general application, temporarily and remarkably increases.
In this time, by increasing the intensity of the stimulating tone source the microphonic potential grows larger and larger.
f) When the exposure of both ears to noise and the curare injection to the unilateral carotis were carried out simulataneoulsy, the decrease of microphonic potential in the injected side, especially atthe lower frequency, was larger than that in the non-injected side.
Next, the observation of an objective audiogram based upon the new point of view by use of conditioned response shows the following results.
g) In the cut group of the tendon of tensor tympani, the loss of hearing power in the cut side, which increases gradually by lengthening the time of exposure to noise, is remarkably large in comparison with that in non-cut side.
In the frequency distinction, the loss in the shorter duration of exposure is larger in the high and middle frequency zones than in the lower one, and that in the longer duration reveals the pattern of C5-dip since the loss at the higher frequency zone in the cut side gradually increases.
h) The normal audiogram of a conditioned dog and the audiogram of the same dog in general anesthesia show that general anesthesia results in the elevation of threshold to the exposure and also in the loss of hearing power especially in the lower and middle frequency zones rather than that in the higher frequency zone.

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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.

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For clarifying the function of tympanic muscles in human beings, the experimental fatigue of acoustic sensation and the acoustic reflex of the tympanic membrane were observed by means of measuring the retraction grade of the tympanic membrane. The retraction grade of the tympanic membrane and fatigue during continuous volley in persons without experience of shooting were observed with the following results.
1). The classification of the acoustic reflex of the tympanic membrane was attempted through the findings of the tympanic membrane.
2). The interrelation between the type of audiogram in fatigue and the acoustic tympanic reflex was clearly made.
3). In tympanic muscles in good condition and in the normal chain mechanism of the ossicles, the conduction of higher tone becomes better by the change of conductive system including the tympanic membrane to the tone and becomes the factor of remarkable loss in higher frequency or of c3 dip. However, the speech area is protected by the slight lesion in the low or middle frequency range.
4). Where the acoustic reflex of the tympanic muscles is bad, it is possible to lose the hearing acuity even in the lower frequency area.
5). Considering the latency of this reflex the protective function of the inner ear to momentary intense sound is doubtful, but it is evident from this experiment that the tonus of this muscle acts protectively in the time of long exposure to the intense sound.

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