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木の音色に関する研究(第 2 報) : 粘性項を考慮した Timoshenko 式による木材音響スペクトルの解析(林学部門) Study on the timber of wood II : Analysis of the sound spectrum of wood using viscoelastic Timoshenko equation (Forestry) 矢野, 浩之 ヤノ, ヒロユキ Yano, Hiroyuki 松久, 寛 マツヒサ, ヒロシ Matsuhisa, Hiroshi 片持ちばり自由端からの放射音圧レベルを, 粘性項を考慮したTimoshenko式を用いて計算し, 繊維方向試料および放射方向試料の音響スペクトルへの比重(γ), 比動的ヤング率(E/γ), tanδ, E/κG値並びに厚さ(h)の寄与について, 広い周波数帯域で検討した。せん断変形の寄与が少ない領域では, ピークレベル(PL)は, PL(dB)=-Alog(γ×tanδ×h×√<E/γ>)の関係で示された。ここで, Aは定数。振動モード次数の増大につれ, ピークレベルは周波数の対数に反比例して減少した。その減少の程度は, 比重, tanδには依存せず, 繊維方向試料, 放射方向試料共に, E/κG値の増大と共に増加した。木材放射音の音色に寄与する因子は, たわみ変形におけるせん断変形の寄与の程度であると推測される。 The dependence on frequency of sound pressure level radiated from the free end of a cantilever was caliculated using viscoelastic timoshenko equation. The effects of specific gravity (γ), specific dynamic Young's modulus (E/γ), tanδ, value of E/κG and height of beam (h) on the sound spectrum for longitudinal and radial specimens were also estimated in a wide frequency range. At lower frequencies, where shearing deformation is negligible, the sound pressure level (PL) could be represented by the following formula : PL (dB)=-Alog (γ×tanδ×h×√<E/γ>) where, A is constant. With elevation of vibration mode, peak sound pressure level decreased linearly as frequency increased logarithmically. The degree of decreased in peak level in both longitudinal and radial specimens was independent of variations in γ and tanδ, whereas it was magnified with increasing value of E/κG. It is speculated that E/κG contributes to the tone quality of radiated sound from wood in proportion to a share of shearing deformation in the deflection of beam. 1991-11-19 jpn departmental bulletin paper https://kpu.repo.nii.ac.jp/records/5193 AN00062275 00757373 京都府立大學學術報告. 農學 The scientific reports of Kyoto Prefectural University. Agriculture 43 24 31 https://kpu.repo.nii.ac.jp/record/5193/files/KJ00000079192.pdf application/pdf 505.6 kB 2017-02-20