On a method for acoustic transmission analysis of air-duct network including reflected traveling waves : Algorithm for personal computers and physical experiments

rights: 社団法人日本建築学会relation: isVersionOf: http://ci.nii.ac.jp/naid/11000417473

Numerical analyses on acoustic performance of dissipative silencers

吸収型消音装置の音響予測について境界要素解析の適用を試みた｡多孔質材料は固定骨格モデルとし,その音響特性として実効音速と実効密度が必要となるため,まず,その測定方法について検討した｡この数値解析手法の有効性については,吸音要素の垂直入射吸音率,また,内貼りダクトやバッフル型スプリッタ-消音装置の音響減衰の予測に適用し,理論値や実験値との比較により確認した｡次に,この数値解析手法を壁体換気開口内周壁内貼り,吸音材ガイド付き膨張管型消音器,サウンドストリーム型消音装置,消音エルボなどに適用し,従来の実験的研究では探求が困難であった吸音要素を含む消音装置内音響伝搬の基礎的性質について多くの重要な知見を得た

[N349] An In-duct Method for Determination of Oblique Incidence Reflection Factors

The free-field methods for determining the reflection factor of a surface lose their validity especially when the incidence angle becomes larger than about 30 degrees and the frequency becomes lower than about 1,000 Hz even though the surface is a homogeneous flat wall, because of the contamination by the diffracted waves from the edges of the truncated test piece. To overcome the difficulties of the free-field methods, an in-duct method has been introduced here. In this method a test piece is installed at one end of a duct, and the cross-modes of interest are excited from the other end. The complex pressure amplitudes of the incidence and reflected waves of each of the modes can be extracted from the sound pressures observed in the duct field. Numerical simulations were carried out using a boundary element approach. The effectiveness of the in-duct method was confirmed by comparing its results to theoretical ones for a locally reacting surface. By using this method, oblique incidence reflection factors have been determined for several surfaces of extended reaction such as a fiberglass-board backed with a rigid wall and a sound-absorbent wedge array.会議名称:The 32nd International Congress and Exposition on Noise Control Engineering主催学会:KSNVE/AS

ACOUSTIC PERFORMANCE OF A SPLITTER DUCT SILENCER WITH ZIGZAG AIRWAYS

会議名称:The 28th International Congress and Exposition on Noise Control Engineering主催学会:INCE/US