In order to evaluate the effect of the therapeutic drugs for sensorineural deafness, it is quite necessary to know the progression of hearing loss without drugs for the control study.
The author described that long-term assessment of hearing loss without therapy has not yet fully known and that we have no appropriate methods to determine the prognosis.
The author made auditory fatigue tests on 20 objects to know the effect of drugs for the sensorineural deafness.
Recovery curves of auditory fatigue obtained here when they took the medicine did not differ from those seen when they did not have it except one case.

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In 1969, the statistical research of the patients with hard of hearing in Tokyo was be done.
The results are as follows.
1) The number of the deaf in all is about 14, 660 (0.133% of all the people lived in Tokyo).
2) They live in suburbs more than in the center of Tokyo.
3) The patients who are presbycusis are in a ratio of 20-70 to a ten thousand.
4) When we devide the class of hard of hearing, the patients with loss of hearing 90dB in both side of the ear are the most of all of the patients.
5) If we classify by the cause, number of the inborn deaf is the most and next is otitis media chronica.
6) The occupations of the deaf are almost bodily labors.
7) Almost of them don't hope the auditory train for speech.
8) One half of them have hearing aids.
Many patients with deafness are inborn, so we hope to discover and diagnosis them in nursling stadium. Though the deaf children cann't hear “speech”, they ought to learn “language” before school. The patients with disturbance of hearing after 8 years old can speak, but not hearing “language”. So that, they cann't communicate with others, and they are solitary. They are engaged as bodily labors and live with scant income. One half of them have hearing aid, but they don't use it sufficiently. They can hear tones but cann't understand the language. We ought to reconform the system of the auditory training, and inform the probabilities of the auditory training.

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Ninety-seven young children were tested their hearing acuities by the behavioral tests and the evoked response audiometry in sleep in 1969. Most of their age ranged from 1 to 3 years old. The chlorpromazine and monosodium trichlorethyl phosphate syrup were given to induce sleep. Ten cases failed to sleep for the first test, but they succeded to sleep for the second test. Fifty-five cases showed their P₂ latencies around 200msec, 15 cases around 250msec and 12 cases 300msec or more.
ERA thresholds of 59 cases were compared with behavior thresholds. The threshold differences revealed that 68% of them were within ±10dB.
Our cases included mentally retarded children, which affected the results of the behavioral tests, and 10 cases showed the lower threshold of more than 10dB in ERA. No conclusion was made about in what degree ERA threshold gave higher threshold than those of the behavioral tests.

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Shadow hearing is, in relation to interaural attenuation, important phenomenon when the true threshold of bone conduction is measured.
The cross perception in bone conduction, Lucae's Gekreuzte Knochen-Empfindlichkeit, is similar to shadow hearing in the way of the perception that the bone conductive sound given monolaterally is heard at the ear of the other side.
Three cases were demonstrated to discuss the difference between these two phenomena, and clinical research showed that these two phenomena are essentially different, except that the shadow hearing with negative interaural attenuation is presumably cross perception of bone conduction.

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Hearing Clinic for Mothers and Children sponsered by Kobayashi Institute of Physical Research was started in Nov. 1956. This clinic offer the following services: (1) Audiological diagnosis (2) Hearing aid selection and fitting (3) One-day classes for parents on Hearing aid (4) Three-months auditory training for infants and young children (0-2yrs old) and for preschool children (3-5yrs old).
Until Feb. 1971 since we started, the total number of children who came for hearing test is 498. The degree of their hearing loss has wide variety, but we noticed the tendency that the children with severe loss came to the clinic earlier than the children with moderate loss.
Among the services we offer, the auditory training using portable hearing aid is our main effort. This is a parentoriented program which we think more suitable for infants and young children than the clientoriented.
Fifty-six children finished our auditory training course. Most of them entered the ordinary primary schools and kindergartens. Their hearing loss is about sixty dB in average.
Besides there are a considerable number of hearing impaired children who live in local district and unable to attend the courses. For them, a correspondence course is available. At present four cases are receiving lessons through this service.

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Vistamycin (VSM) is a new aminoglycoside antibiotic produced by Streptomyces ribosidificus and effective against gram positive and negative bacteria. The present experimental study was made on 63 guinea pigs to compare the ototoxicity of VSM with those of Kanamycin (KM) and Dihydrostreptomycin (DHSM). These guinea pigs of Hartley strain (300g at the start of injection) were divided into 6 groups. Dosis of the administered antibiotics and number of the animals in each group were as follows: VSM 200mg/kg group (14), VSM 400mg/kg group (12), KM 200mg/kg group (14), KM 400mg/kg group (10). DHSM 200mg/kg group (10) and DHSM 400mg/kg group (3). Each antibiotic was injected intramuscularly for 28 days. Before, during and after the injection of these antibiotics, Preyer's pinna reflex test was carried out with audiometer with frequency range from 500Hz to 10, 000Hz. After the last injection the animals underwent vital perfusion with physiological saline solution and then with Wittmaack's fixative. Bilateral temporal bones were removed from the skull and fixed in the same fixative further for several days. According to the conventional method, serial celloidin horizontal sections were prepared and stained with hematoxylin-eosin. Histopathological examination revealed that the loss of the most sensitive outer hair cells of the organ of Corti occurred less frequently as well as less extensively in the guinea pigs received VSM at the dosis of 200mg/kg or 400mg/kg than in the animals received KM at the same dosis. DHSM was less ototoxic than the another two antibiotics at the dosis of 200mg/kg.
The present study indicated that VSM is less ototoxic than KM.

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Speech audiometry, as compared to pure tone audiometry, is of special importance since it directly evaluates subject's ability of speech perception, and has broadened the area for the differential diagnosis of retrocochlear deafness. Natural speech sounds used in conventional speech audiometry, however, impose serious limitations upon the reliability of results because of the variability in human utterances and the difficulty in the exact specification of their acoustic characteristics. On the other hand, synthetic speech sounds are ideally suited for this purpose since their acoustic characteristics can be exactly specified and easily controlled. Identification tests were performed on 100 cases of sensorineural hearing impairment using synthetic vowels. Analysis of response patterns in the F₁-F₂ plane leads to a classification of these cases into 4 types. The relationship between these types and thepure tone audiograms are examined, which indicates close correlation of response patterns and audiograms, in cases of Type 1 and Type 2.
1. Introduction
Although the pure tone audiogram provides an accurate means of investigating the subject's absolute threshold of hearing, it does not provide enough information as to the ability of speech perception in hearing-impaired patients. Speech audiometry, on the other hand, is intended to evaluate directly the subject's ability of speech perception, and has broadened the area of differential diagnosis of sensorineural deafness.
Natural speech sounds used in conventional speech audiometry, however, impose serious limitations upon the quantitative interpretation of the results, because of the variability in human utterances and the difficulty in exactly specifying their acoustic properties. These difficulties can he overcome by using synthetic speech sounds as test stimuli, since their acoustic characteristics can be exactly specified and easily controlled, so that not only typical sounds, but also a whole continuum of speech sounds can be generatedd and the subject's performance can be investigated in detail.
The present study is an attempt toward utilization of synthetic speech sounds for the purpose of standardizing the procedures for the evaluation of sensorineural hearing impairments. Synthetic vowel stimuli with various combinations of the first and the second formant frequencies (F₁ and F₂) were generated by a terminal-analog speech synthesizer, and were used for speech audiometry. The results of identification tests on subjects with sensorineural hearing impairments as well as with normal hearing are analyzed. Cases of sensorineural deafness are shown to be classified into four types on the basis of their characteristic patterns of response in the F₁-F₂ plane. Correlation between these types and their pure tone audiograms are examined.
2. Experimental Procedures Stimuli
The synthetic vowels were produced by a terminal analog speech synthesizer. The fleck diagram is shown in Fig. 1. A train of shaped pulses was used as the glottal source, and was fed to a cascaded connection of circuits representing the higher pole correction, the radiation characteristic and four formant characteristics. The fundamental frequency was set at 140Hz. The first and the second formants were used as variable parameters, while the third and the fourth formants were held constant at 2, 700 and 3, 500Hz. A set of 64 synthetic vowel stimuli was chosen by the combination of F₁ and F₂ values as shown in Table 1, The duration of each test sound was 800msec, and the rise time constant for pitch and intensity was 20msec. These sounds were recorded on tape in random order and were presented monaurally to each of the subjects through an earphone in a sound-proof room. The intensity of sound stimuli was kept at the Most Comfortable Level for each subject, which turned out to be between 80 to 100dB in sensation

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