論文

2018年4月1日

地表面上の点音源による音場の拡張・局所作用理論モデル解析および有限差分数値解析の適用性に関する検討

日本建築学会環境系論文集
  • 大嶋 拓也
  • ,
  • 黒坂 優美

83
746
開始ページ
355
終了ページ
363
記述言語
英語, 日本語
掲載種別
研究論文(学術雑誌)
DOI
10.3130/aije.83.355
出版者・発行元
日本建築学会

 The problem of sound field from a point source in the static air above an absorptive ground surface has been extensively studied in literature as the setting is typical for outdoor sound propagation. Most of the theoretical models that deal with the problem are classified as either extended reaction models that are considered physically exact, or local reaction models that are considered approximations. Especially, approximations assuming the local reaction are introduced in many models. However, the validity of the assumption is elucidated through comparison with the extended reaction models only in limited cases. This is because the reliability of the extended reaction models are difficult to be assured as the derivation process of the extended reaction models are generally complex and sometimes unintentionally transforms the models to local reaction models. In contrast, with the advancement of numerical simulation techniques, a numerical model based on a finite-difference time-domain method that solves the propagation above and under the ground surface simultaneously by handling the soil under the ground surface as a porous medium has been proposed by Salomons. The numerical model is regarded as an extended reaction model because the model solves the propagation under the ground surface. Hence, the reliability of the extended reaction models can be assured through mutual comparison of the numerical and the extended reaction models. However, the comparison has only been made under limited conditions of low effective flow resistivities and short-range propagations under low frequencies. The applicability to high effective flow resistivities and long-range propagation under medium and high frequencies remains to be an open question.<br> In the present study, the validity and applicability of an extended reaction model by Di, a local reaction model by Di, an asymptotic local reaction model by Kawai and the aforementioned finite-difference time-domain numerical model are tested. Main variables are the frequency, the effective flow resistivity under the ground surface, the source height and the source-receiver horizontal distance, which are chosen to be in ranges of 125 Hz–4 kHz, 75–20 000 kPa·s/m<sup>2</sup>, 0.3–2.4 m and 5–80 m, respectively. The validity of two-dimensional modeling is tested and the two-dimensional modeling is applied for the numerical model because vast domain sizes are required. From the results, the followings are found.<br> 1. The validity of the tested extended reaction model is confirmed under low effective flow resistivity conditions from a good match between the extended reaction and the numerical models.<br> 2. The local reaction is considered as a valid assumption within the tested variable ranges because the maximum difference between the extended and local models are 1.2 dB.<br> 3. The asymptotic local reaction model is applicable within the tested variable ranges because the two local reaction models are excellent match.<br> 4. The numerical model differs from the extended and the local reaction models under low source height, long range and high effective flow resistivity conditions. From a further investigation, it is found that the difference is possibly due to the handling of the medium interface in the numerical model. Using a local reaction boundary condition that takes the frequency characteristics of the boundary into account can be a potential solution.

リンク情報
DOI
https://doi.org/10.3130/aije.83.355
CiNii Articles
http://ci.nii.ac.jp/naid/130006729027
ID情報
  • DOI : 10.3130/aije.83.355
  • ISSN : 1881-817X
  • ISSN : 1348-0685
  • CiNii Articles ID : 130006729027
  • identifiers.cinii_nr_id : 9000389444098
  • SCOPUS ID : 85047242711

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