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Volume 28 , Issue 6
Showing 1-11 articles out of 11 articles from the selected issue
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INVITED REVIEW
  • R. R. K. Jones
    Volume 28 (2007) Issue 6 Pages 367-374
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    The control of environmental noise is becoming of increasing importance to the European Commission. As a result, they have recently instigated a set of legislative initiatives in order to prevent increases in noise exposure for the population and, where possible, to reduce that exposure. This paper introduces current European Union environmental noise policy, as implemented through the Environmental Noise Directive of 2002, and describes the work of the related research projects “HARMONOISE” and “IMAGINE.” The paper then focuses on railway-specific issues, with detail of the railway noise prediction methodology developed within these projects, including the source database that is now in place. In parallel, the Commission has introduced, within railway Technical Specifications for Interoperability, noise emission limits for new and refurbished trains, as a means of progressively reducing railway noise at source. The noise elements of these Specifications are described and discussed.
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PAPERS
  • Masamichi Oikawa, Kazuhiko Ohta, Kouki Okabe, Itaru Morishita, Hisayuk ...
    Volume 28 (2007) Issue 6 Pages 375-384
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    A measurement of low-frequency reverberation was conducted in order to investigate features of sea surface and bottom scatterings in shallow water, where it is generally difficult to acquire sea surface and bottom reverberations separately. In the measurement, a vertical line array receiver is used so that reverberations scattered from the sea surface and bottom over a wide range of grazing angles are captured with multibeams covering a vertical plane. The parameters of the sea surface and bottom scattering functions are estimated by applying the stochastic inversion method to solve the forward problem involving the measured reverberation and its modeling result calculated using the sea surface and bottom scattering functions. The estimated parameters produce a modeling result that is in good agreement with the measured reverberation for each beam, and describe sea surface and bottom scattering strengths as functions of grazing angle via the scattering functions.
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  • Junji Yoshida, Hiroshi Hasegawa, Masao Kasuga
    Volume 28 (2007) Issue 6 Pages 385-391
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    In the present study, we investigated the effect of a previous sound on loudness at the absolute threshold of hearing. The change in the absolute threshold of hearing was measured when a pure tone preceded the test tone for the measurement of the threshold. The previous sound at 60 dB SPL was presented first in one ear, followed by the presentation of the test tone in either the contralateral or ipsilateral ear after an interval of 0.5 s. Both the previous and test sounds had the same frequency, 500 Hz, and the same duration, 3 s. The change in threshold was obtained from the difference between the thresholds with and without the previous sound. As a result, the threshold was found to decrease significantly by approximately 2 dB when the previous sound was presented in the contralateral ear. On the other hand, the threshold was only slightly changed when the previous sound was presented in the ipsilateral ear.
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  • Hideyuki Nomura, Tetsuo Funada
    Volume 28 (2007) Issue 6 Pages 392-402
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    The purpose of the present paper is to clarify the effects of unsteady glottal flow on phonation. We perform numerical experiments with respect to vocal cord vibrations in order to verify the validity of the proposed model for a glottal sound source. In addition, the prediction of pressure waves induced by unsteady glottal jets is attempted. Good agreement between the numerical results and the measured data of the properties of the glottal source indicates that the proposed model is a good tool for the analysis of speech production. Simulated pulsatile glottal jets show the generation of high-frequency noises in a pressure wave at the glottis and the unsteady and asymmetric motion of vortices. These vortices cause amplitude fluctuations in the pressure wave downstream near the glottis, although pressure waves far from the glottis are not greatly affected. In conclusion, the unsteady glottal flow affects only the area near the glottis and does not greatly affect speech waves radiating from the mouth.
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  • Hideyuki Nomura, Tetsuo Funada
    Volume 28 (2007) Issue 6 Pages 403-412
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    In the present paper, the effects of the false vocal folds (FVFs) on sound generation induced by an unsteady glottal jet through a two-dimensional rigid wall model of the larynx are investigated by conducting numerical experiments. The glottal jets are simulated by solving the basic equations for a compressible viscous fluid based on the larynx model with and without the FVFs. The existence of the FVFs increases the amplitude of noise-like pressure fluctuation at the glottis and faraway from the glottis. Furthermore, the FVFs give rise to the broadbanding of the pressure spectrum throughout the fluid domain. These results indicate that the FVFs have a profound effect on the generation of broadband noise components in a speech wave.
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  • Dongwen Ying, Yu Shi, Xugang Lu, Jianwu Dang, Frank Soong
    Volume 28 (2007) Issue 6 Pages 413-423
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    In this study, we propose a voice activity detector (VAD) based on a noise eigenspace, which improve the robustness of VAD by utilizing the compression capability of the eigenspace. A noise eigenspace is constructed by using eigenvalue decomposition of the noise correlation matrix. When noisy speech is projected into the noise eigenspace, the noise energy is packed into a few dimensions with large eigenvalues, and those dimensions hopefully possess relatively less speech, because the speech energy distribution is usually different from noise energy distribution. The noise can be reduced by discarding those dimensions with large noise energy, while no significant loss occurs in speech. To track noise variation, the noise eigenspace is periodically updated, where the computation cost for eigenspace construction can be kept at an acceptable level. The proposed VAD was evaluated using the TIMIT database mixed with several noises. The experiment showed that the proposed VAD is more accurate than previous VADs in noisy environments.
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  • Koichi Uchida, Kenshi Kishi
    Volume 28 (2007) Issue 6 Pages 424-430
    Released: November 01, 2007
    JOURNALS FREE ACCESS
    In this paper, we focus on the control of the tone of a glass harp during the process of manufacturing, and on the analysis of the vibration of the glass harp using a finite element method. First, the effect of various factors on results is studied, such as the element type that enables a good geometries approximation and the number of divisions on the accuracy of mode frequencies. Second, we examine how each mode frequency changes with the bulge of the glass harp. The results demonstrate that the use of a bulge is effective in controlling the pitch and the timbre. Third, the pitch can be varied over a wide range by changing the bulge of the cup. In particular, it can be finely adjusted by cutting the inside bottom of the cup so as to form of a small circular groove instead of using a conventional method, which involves cutting the outside of the cup.
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