Acoustical Science and Technology
Online ISSN : 1347-5177
Print ISSN : 1346-3969
ISSN-L : 0369-4232
Volume 43, Issue 6
Displaying 1-7 of 7 articles from this issue
PAPER
  • A. J. Patitsas
    2022 Volume 43 Issue 6 Pages 297-305
    Published: November 01, 2022
    Released on J-STAGE: November 01, 2022
    JOURNAL FREE ACCESS

    It is verified that the source of the acoustic emissions when beach sand or other squeaky grains are stepped on or impacted by a pestle lies in a thin shear band directly under the pestle. The grain layers in this band slide one over another at a slow creepy pace giving rise to energy transfer, via the stick-slip effect, from the impacting pestle to the elastic vibrations in the shear bands at the grain contact areas. In turn, this vibration energy feeds the elastic modes of vibration along the vertical grain columns or equivalently, the elastic modes of vibration in the shear band under the pestle comprising the vibrating columns, with dominant frequency in the range of 1,000 Hz. In search of an explanation of the acoustic emissions when booming dune sand is pushed by a blade or is freely avalanching, we adopt the concept of the collision shear band, where, due to the high degree of fluidity of the sand mass, the grain layers slide one over another at a brisk pace so that the average collision frequency between grains in two adjacent grain layers defines the dominant frequency of the acoustic emission in the range of 100 Hz.

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TRANSLATED PAPER
  • Zhi Zhu, Miho Kawamura, Masashi Unoki
    2022 Volume 43 Issue 6 Pages 306-315
    Published: November 01, 2022
    Released on J-STAGE: November 01, 2022
    JOURNAL FREE ACCESS

    It has been known that noise and reverberation greatly affect the perception of linguistic information, in particular speech intelligibility. However, the effect of noise and reverberation on the perception of non-linguistic information has not been clarified. We investigated how these types of disturbances affect the perception of non-linguistic information (speaker individuality and vocal emotion) of noise-vocoded speech. We conducted speaker-distinction and vocal-emotion-recognition experiments using noise-vocoded speech created from the speech in noisy, reverberation, and noisy reverberant environments as stimuli. We used seven noise conditions (signal-to-noise ratio (SNR) = ∞,20,15,10,5,0,−5 dB) and six reverberation conditions (reverberation time (TR) = 0.0,0.1,0.3,0.5,1.0,2.0 s). In both speaker-distinction and vocal-emotion-recognition experiments, the main effects of noise and reverberation were significant, but the interaction was not significant. From these results, except for extremely poor sound conditions, under daily noise and reverberation conditions (an SNR of more than 10 dB and TR less than 1.0 s), there were no significant effects of noise and reverberation.

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TECHNICAL REPORTS
  • Ryuta Tomita, Yuta Goto, Dai Adachi
    2022 Volume 43 Issue 6 Pages 316-321
    Published: November 01, 2022
    Released on J-STAGE: November 01, 2022
    JOURNAL FREE ACCESS

    When an accelerometer is placed on a soft floor covering such as a carpet, a resonance system is created by the spring of the carpet and the mass of the accelerometer, and vibrations are amplified at the resonance frequency. This is called "contact resonance." Therefore, to accurately measure the vibration of the floor structure underneath the carpet, it is generally necessary to first peel off the floor covering. Contact resonances on surfacing materials such as carpets and tatamis must be considered when measuring the vibration of buildings. The German standard is DIN 45669-2. In this report, we present a comparison of the method specified in DIN 45669-2 and a method using vibration control rubber proposed in this study. Measurement results showed that, when using the DIN 45669-2 method, there was almost no contact resonance effect for the thinnest carpet, but for other carpets, a contact resonance effect was observed. The values estimated by the method using the vibration transmission rate of vibration control rubber showed that the contact resonance effect can be reduced for the carpets examined in this study.

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  • Shigeaki Amano, Yukari Hirata, Kimiko Yamakawa
    2022 Volume 43 Issue 6 Pages 322-326
    Published: November 01, 2022
    Released on J-STAGE: November 01, 2022
    JOURNAL FREE ACCESS

    Several previous studies in speech production obtained a boundary of two phoneme categories by an exhaustive search for the "optimal boundary" that provides the best phoneme classification on an acoustic dimension such as voice onset time. However, they used this method without confirming its accuracy in estimating the true boundary. The present study examined this accuracy by conducting a Monte Carlo simulation under several conditions of the means and variances of two phoneme categories. The results revealed that, compared with the statistically estimated boundary, the "optimal boundary" tended to have bigger root mean square errors from the true category boundary. This finding indicates that the "optimal boundary" is less accurate than the statistically estimated boundary for estimating the true boundary. Our study considers the limitations of the previous method and recommends a statistically estimated boundary in future investigations.

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  • Yoshihiro Miyata, Takuya Asami, Hikaru Miura
    2022 Volume 43 Issue 6 Pages 327-334
    Published: November 01, 2022
    Released on J-STAGE: November 01, 2022
    JOURNAL FREE ACCESS

    Conventional ultrasonic welding uses linear vibrations, but welding using an elliptical locus improves welding strength. Therefore, we developed a vibration source that generates an elliptical locus using a single longitudinal vibration transducer. Although vibration sources with an elliptical locus have been reported previously, they were designed using the equivalent transmission line method. In this paper, we used the finite element method to elliptical vibration source design, and we fabricated a vibration source and measured its characteristics. Bringing the resonance frequencies of the longitudinal and torsional vibration closer together allowed vibration with an elliptical locus to be obtained at a single frequency.

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