Design theory for acoustic metamaterials based on transmission-line theory and its applications to acoustic cloaks

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K14132
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29030:Applied condensed matter physics-related
• Research Institution: Kagoshima University
• Principal Investigator: Nagayama Tsutomu 鹿児島大学, 理工学域工学系, 助教 (80781997)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: 変換音響学 / 音響透明マント / 音響メタマテリアル / 回路モデル

Outline of Final Research Achievements

In this research, the design theory for acoustic metamaterials has been proposed based on the transmission-line theory. The theory of the circuit model for electromagnetic metamaterials has been extended to acoustic metamaterials, and correspondences between material parameters and circuit parameters have been revealed. An acoustic carpet cloak for hiding an object on a flat surface has been designed by using the circuit model, and its operations have been confirmed by circuit simulations. Also, design formulas for acoustic metamaterials equivalent to the circuit model have been derived, and an acoustic carpet cloak for hiding an object on a flat surface has been designed as an example. Sound pressure level field distributions have been calculated by using a COMSOL Multiphysics, and operations of the designed acoustic carpet cloak have been shown from the calculated results. Therefore, the validity of the proposed design theory for acoustic metamaterials can have been confirmed.

Free Research Field

音響メタマテリアル, マイクロ波工学, 電磁メタマテリアル

Academic Significance and Societal Importance of the Research Achievements

本研究の成果により,座標変換に基づく高度な音波の経路制御を実現可能な音響メタマテリアルを回路モデルを用いて設計することが可能になった.これにより,従来の反射等を用いる音波の経路制御に比べて遥かに自由度が高い,新たな音波制御技術を開拓できる可能性がある.また,音響メタマテリアルの構造パラメータも大量の数値計算に頼らずに設計式から一意的に決められるため,非常に画期的である.また,本研究により電信方程式と音響方程式の双対性から,材料パラメータと回路パラメータの対応関係を明らかにしているが,同様の考えを適用すれば波及効果として,水波や地震波などの異分野の流体解析や設計への展開も期待できる.