著者

小松崎 俊彦 岩田 佳雄

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集C編 (ISSN:18848354)

巻号頁・発行日

vol.78, no.786, pp.420-430, 2012 (Released:2012-02-25)

参考文献数

10

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In this study, a virtual sound production system is developed where the difference frequency component appears as the secondary audible sound at a point of interference locally by the nonlinear interaction of two independently radiated ultrasounds while they travel directionally and intersect each other. The design of high-directive ultrasonic radiator, followed by the investigation of virtual sound production performance has been done theoretically as well as experimentally. It is known from these investigations that the fairly local sound reproduction in free space is possible, yet the sound pressure level of the secondary field is small. The results have also shown that the generated virtual sound area is dependent on both the difference frequency and the intersection angle of two carrier waves emitted by two sound sources.

著者

小松崎 俊彦 畑中 健介 岩田 佳雄

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 C編 (ISSN:03875024)

巻号頁・発行日

vol.74, no.737, pp.75-82, 2008-01-25 (Released:2011-03-04)

参考文献数

14

被引用文献数

3 3

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Recent advances in digital signal processors have facilitated the development of active noise control (ANC) technology where the various kinds of researches as well as applications have been studied. In general, the sound waves propagate spherically in three dimensional space. Simply constituting SISO system using ordinary loudspeaker as a control source may cause interfered sound field with both attenuated and amplified nodes exist. By placing number of microphones and control sources can improve the range of quiet zone and many researches have been dedicated to this end, yet still limitations on implementation and cost cannot be neglected. On the other hand, the recent development of high-directional loudspeakers based on new sound production theory known as 'parametric array effect' has allowed sound transmission to a narrow range of acoustic space like 'spotlight'. This peculiar characteristic can be implemented as one measure for improving active noise control scheme controlling acoustic field locally without adversely influencing vicinal space. In the present study, a new approach for active control of sound in free space is developed using high directional parametric loudspeaker as a control source. Experiments are performed for the active control of noise generated by single source located in space, where the noise is attenuated by a control source at error microphone which evaluates sound level. Both normal and the parametric loudspeakers are tested as control sources and results are compared based on measurement of interfered sound field around the evaluation point. It is known that the suggested ANC system can mitigate sound locally but cause less influence on sound field in circumferential space.

著者

本江 哲行 佐藤 秀紀 岩田 佳雄 小松崎 俊彦

出版者

日本学術会議 「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」

雑誌

理論応用力学講演会 講演論文集 第52回理論応用力学講演会 講演論文集

巻号頁・発行日

pp.202, 2003 (Released:2003-03-25)

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ゴルフボールの飛距離に影響を与えるスピンに関する研究が多く行われているが,ロフト角,摩擦係数,反発係数,ボールの慣性モーメントなどのパラメータが衝突中のスピンに与える影響が明確になっていない. そこで,本研究では,先に提案したボールの材料の物性値と形状を考慮できる衝突モデルを用い,滑りと回転を考慮するために衝突モデルにスライダーと接線方法のばねを付加し,ゴルフボールとフェイスの斜め衝突のシミュレーショを行う.そして,ロフト角や摩擦係数,反発係数,慣性モーメントなどのパラメータと衝突特性の関係を調べる.

著者

小松崎 俊彦

出版者

金沢大学

雑誌

若手研究(B)

巻号頁・発行日

2006

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本研究は,騒音の存在する自由音場において,高指向性スピーカを利用して局所的に騒音を低減し,無指向型スピーカでの場合のように,周辺空間に余分な音の増大を招くことなく静音化を実現する能動騒音制御システムの開発を目的とする.本年度は,前年度に検討したパラメトリックスピーカの指向性,および干渉音場の実験結果を踏まえて,それらを数値的に予測する理論モデルを構築し,さらに,必要な空間だけを局所的に静音化する能動騒音制御システムの実証実験を行った.まず,数値的検討については,パラメトリックアレイに関する理論モデルに基づき,波動方程式による数値計算モデルを構築した.生成される音圧の空間分布および騒音源との干渉音場特性について数値的に予測し,実験結果との定性的な一致を得た.本モデルによって,音波の高指向性をある程度再現可能であることが示されたが,実測値ほどの高指向性の再現は困難であった.これは計算過程を簡略化するための近似が主な要因であると考えられる。さらに,以上の結果を踏まえて,騒音源を模した無指向型スピーカから制御対象音を出力し,パラメトリックスピーカを制御音源として,目標点に設置したマイクロホンにおける音圧値を最小にするように制御音を生成可能なシステムを構築した.パラメトリックスピーカの再生音が非線形効果によるものであることを考慮して,非線形特性を同定可能なニューラルネットワークを採用した.周期的騒音の発生を想定した制御実験を行い,干渉音場計測により周辺音場への影響などについて調べた.制御音源として無指向型スピーカを用いた場合と比較して,目標点周辺への影響が少ない制御が可能であることが実験的に示された.

著者

程 輝 岩田 佳雄 小松崎 俊彦 佐藤 秀紀

出版者

一般社団法人日本機械学会

雑誌

セルオートマトン・シンポジウム講演論文集

巻号頁・発行日

vol.2001, pp.246-249, 2001-11-14

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Recently, Cellular Automata has been rapidly developed and widely used for analyzing many complex problems. In this paper, the phenomena that the sand grain which is initially and randomly spread on the surface of a square plate will crowd around some positions to generate shape of nodal line at natural modes is simulated by using Cellular Automata. Two moving patterns of sand grain are presented, one is the rolling of sand grain at micro-vibration condition or no-vibration position, and another is jump of sand grain at violent vibration or natural vibration condition. The former obeys usual Moore neighborhood rule, and the latter is defined that the jump distance is proportional to the initial vibrant velocity of plate in two directions of plate plane. The calculated procedures are list as following : first, a plate plane is divided into some uniformed grids in which the height of sand grain is defined as a state variable to be discussed in this paper ; then the height of sand grain caused its rolling movement is calculated ; finally, according to above-mentioned rules the height change of sand grain due to jump movement is calculated. The periodic boundary condition is used in simulation. The simple-supported condition at four boundary sides of the plate is mainly analyzed in this paper. In this case, the function of vibrant mode is directly used, and the mode shape is first shown ; then the Chladni's Figure which describes the distribution of sand grain in the plate surface is calculated by CA. Finally, using the same rule to simulate other constrained plates, such as free-boundary-condition and fix-boundary-condition. Two calculated results at mode order M=N=2 are shown in this paper. Due to the periodic boundary condition, sand grain will stack at four boundaries. But useful stacked shape should be observed in central wide area of plate. From calculated results of height distribution figures (Chladni's Figure) of sand grain in different constrained boundaries and mode situations, the nodal line at natural mode condition is clearly seen. Finally, the fact that CA is a useful method to describe the vibration mode is evidenced.