Journal of the Acoustical Society of Japan (E)
Online ISSN : 2185-3509
Print ISSN : 0388-2861
ISSN-L : 0388-2861
Volume 2, Issue 4
Displaying 1-5 of 5 articles from this issue
  • Otohiko Nomoto, Akiji Ouchi
    1981 Volume 2 Issue 4 Pages 181-196
    Published: 1981
    Released on J-STAGE: February 17, 2011
    JOURNAL FREE ACCESS
    On the basis of the normal mode theory using Mathieu functions it is pointed out by analytical and computational means, that there exists a “complementarity relation” between two definite order spectra under common incidence angle. The O-order makes complementarity pair with the Bragg order (-nB order). The k-th order makes complementarity pair with the-(nB+k) th order, where-(nB/2)<k<∞. The spectra making complementarity pair are associated in the meaning that the higher maximum of one of the components corresponds very low intensity of the other. Lower maximum, however, may occur at the same time for both spectra.
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  • Antonio Moreno, Julian G. Zaragoza, Felipe Alcantarilla
    1981 Volume 2 Issue 4 Pages 197-202
    Published: 1981
    Released on J-STAGE: February 17, 2011
    JOURNAL FREE ACCESS
    Flutter echoes in enclosures with spherical domes are analysed by means of a ray model. After the conditions for the settlement of flutter are established, a ray model is developed to inquire about the achievement of these conditions in enclosures. The model is applied to explain the flutter echo formation in enclosures including a flat floor and a spherical dome, for R/H ranged up to 4 that include most common situations (R is the dome radius and H the dome height from the floor). The characteristics of the flutter echoes suggest the adequacy of using reflectors for destroying that acoustical phenomenon. Information about size and position of reflectors is also obtained from the ray model. Some experiments on a full size enclosure and on a 1: 20 acoustic scale model are also reported.
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  • Kazuo Matsuuchi, Tsutomu Adachi
    1981 Volume 2 Issue 4 Pages 203-211
    Published: 1981
    Released on J-STAGE: February 17, 2011
    JOURNAL FREE ACCESS
    A theory is presented for the discrete-frequency noise generated from axial-flow fans and compressors. The theory describes the noise generation from the fluctuating forces on either rotor or stator blade rows due to the interactions with the adjacent upstream and/or downstream blade rows. The present aim is to give a qualitative description of the total acoustic power for the noise without obtaining the powers for each discrete noise component. For this purpose, a far-field equation is derived from the Ffowcs Williams-Hawkings equation on the assumption that the rotor tip Mach number is small. The equation is utilized in deriving an expression for the total acoustic power. It is shown that the acoustic power includes the important parameters in the study of noise reduction such as the direction of force, the number of blades, and the angular velocity.
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  • Sei-ichi Nakagawa, Toshiyuki Sakai
    1981 Volume 2 Issue 4 Pages 213-230
    Published: 1981
    Released on J-STAGE: February 17, 2011
    JOURNAL FREE ACCESS
    We have developed a real time phonetically based spoken word recognition system on a mini-computer and arecognition equipment which consisted of a filter bank and amicrocomputer. If the vocabulary size of the word recognition system is enlarged to about several hundreds, not only the recognition time becomes very long by increasing an amount of processing but also the correct rate of recognition decreases. To cope with these weak points, we adopted the method which reduced candidate words in the vocabulary by means of pre-matching using both local and global features of a spoken word. Our system is based on the phoneme classification, that is, hierarchical linguistic knowledge. To extend this approach to connected word srecognition, we developed a word boundary detection method by using the pitch and energy contours. In an experiment on the recognition using 100 Japanese city names or ten digits, the system recognized the names (digits) correctly at the rate of 84%(98%) for unspecific speakers and recognized two connected digits at the rate of 83% in real time. Furthermore, we constructed a special equipment of speech recognition which was based on the system. In experiments on word recognition of 32 city names, the recognizer recognized them correctly at the rate of 93.4-94.4% for unspecific male and female speakers.
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  • Y. Yasumoto, K. Kondo, A. Sawaoka
    1981 Volume 2 Issue 4 Pages 231-233
    Published: 1981
    Released on J-STAGE: February 17, 2011
    JOURNAL FREE ACCESS
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