THE JOURNAL OF THE ACOUSTICAL SOCIETY OF JAPAN
Online ISSN : 2432-2040
Print ISSN : 0369-4232
Volume 11, Issue 2
Displaying 1-12 of 12 articles from this issue
  • Article type: Article
    1955 Volume 11 Issue 2 Pages 83-
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
    JOURNAL FREE ACCESS
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  • [in Japanese]
    Article type: Article
    1955 Volume 11 Issue 2 Pages 85-86
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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  • Takuro Ikeda
    Article type: Article
    1955 Volume 11 Issue 2 Pages 87-95
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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    Barium titanate ceramics accompanies the generation of a considerable amount of heat when used as generators of high power ultrasonics. The temperature rise of the ceramics during ultrasonic radiation was measured for the purpose of elucidating the mechanism of the heat generation. When the frequency was varied at constant voltage, large temperature rise was found in the neighbourhood of its resonance. When the specimen was not polarized, it showed no anomalous temperature rise. Accordingly it was concluded that heat is generated by large internal friction. A phenomenological treatment was performed by choosing the strain and the polarization as independent variable and introducing a frictional term proportional to the strain velocity in the piezoelectric equations. Acoustic power and the distribution of heat generation in the ceramics were calculated and the resistance term in the equivalent electric circuit was found to be the sum of the acoustic radiation resistance and the internal friction resistance. Experimental results are explained qualitatively by this theory.
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  • Kazuo Ikegaya
    Article type: Article
    1955 Volume 11 Issue 2 Pages 95-102
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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    When a rigid movable sphere is put into the sound field, the sound pressure acts on this sphere and causes it to vibrate. In this case the velocity of vibration is proportional to the magnitude of incident sound pressure. Applying this principle, we can develop a spherical velocity-microphone. But its velocity depends upon the product of radius of the sphere and frequency of incident sound waves, and also upon the ratio of densities of sphere and medium. Therefore, in designing these microphones it is necessary to estimate the magnitude and frequency character of its velocities, i. e. , frequency response of its sensitivities. In this paper, we have estimated these values from the solutions of the wave equation which satisfy the boundary conditions of vibration. And then we obtained the relation among the vibromotive force acting on the fixed obstacle, the radiation impedance presented by the vibrating obstacle, the mass of the obstacle, and the velocity of the vibrating obstacle. This relation can be applied to estimate the velocity of any movable sphere from the vibromotive force, the radiation impedance and the mass for its sphere, and these results were found to coincide with above calculation.
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  • Michinari Okamoto, Shoozo Kawamura, Shigekazu Tsubaki, Ichiro Oowada
    Article type: Article
    1955 Volume 11 Issue 2 Pages 102-108
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
    JOURNAL FREE ACCESS
    The effects of ear defenders have been experimentally investigated. Seven kinds of various defenders were used in this experiment. The methods and results are as follows: 1. The intensity of sound transmitted through the ear defender was measured in the sound proof room with the artificial ear. In this experiment, the artificial ear constituted of an acoustic coupler and a condenser microphone was set in front of the speaker. The sound from the speaker was controlled by an automatic device. From the result, the ear defenders are divided into two groups; the one is the group which is effective only in the higher frequencies, while another in all auditory frequencies. 2. The auditory threshold for pure tones was measured when one was applied with or without the ear defender. Five healthy men were employed as objects. The objects sat down at the distance of one meter from the speaker. The variation of auditory threshold when wearing the ear defender are the same, notwithstanding the types of defenders. That is, the elevation of threshold are only 20-30db in the frequency range higher than 1000 cps. 3. Recruitment phenomena are positive in masked ears by the thermal noise, but negative in ones with defenders. 4 The ears masked by the thermal noise, and that with the defenders, have recruitment phenomenon, but this phenomenon is weaker than in case of just masked ears.
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  • Noriko Torii
    Article type: Article
    1955 Volume 11 Issue 2 Pages 108-114
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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    This paper describes the articulation tests with English speech sounds which were conducted with the purpose of examining the hearing ability of English language by Japanese students, using eight college students as listeners, and as speakers: an American and a Japanese professor and a student. Every syllable used in the tests were of a conventional c-v-c type. The system used was the low-pass filter system (no filter, 1500cps and 3050cps cut-off)with three kinds of attenuation (0, 15 and 30 db). Though the vowel articulation scores in this test were found to be lower than those of American data, it is noticed that Fletcher's methods of calculating syllable articulation scores from sound articulation sores can be applied to the present data (Fig. 6). While listener's individual differences were large, it seems that speakers' difference did not influence the scores significantly. Inspection of the details of the data shows that the scores were low for the sounds like v, a, v, 1, θ which have no counterparts in Japanese speech sounds.
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  • Masaru Okahara
    Article type: Article
    1955 Volume 11 Issue 2 Pages 115-118
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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  • Kiyoteru Ishii
    Article type: Article
    1955 Volume 11 Issue 2 Pages 118-122
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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  • Kiyoshi Yuyama
    Article type: Article
    1955 Volume 11 Issue 2 Pages 123-124
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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  • Ichiro Kirikae, Shoozo Kawamura
    Article type: Article
    1955 Volume 11 Issue 2 Pages 125-128
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
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  • [in Japanese]
    Article type: Article
    1955 Volume 11 Issue 2 Pages 129-130
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
    JOURNAL FREE ACCESS
    Download PDF (434K)
  • [in Japanese]
    Article type: Article
    1955 Volume 11 Issue 2 Pages 130-131
    Published: June 30, 1955
    Released on J-STAGE: June 02, 2017
    JOURNAL FREE ACCESS
    Download PDF (479K)
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