Title: Theory and calculation for acoustic radiation mode of weak coupled enclosure

Author(s): MAO Rongfu; SU Changwei; ZHU Haichao;

Affiliation(s): Institute of Noise & Vibration, Naval University of Engineering; National Key Laboratory on Ship Vibration & Noise

Abstract: Active structural acoustic control (ASAC) is an efficient method in acoustic radiation control of coupled enclosure. In the past research of ASAC, the concept of "acoustic radiation mode(ARM)of coupled enclosure" was proposed, which was a set of bases functions of structural mode amplitude. However, there was an incompatibility with the ARM definition in free space radiation case which was a set of basic functions of normal velocity or pressure on the vibrating surface. Also, there was severe inconvenience for application as structural modes were required while accurate and useful structural modes were difficult to be extracted in practice. To overcome these problems, by analogy to ARM theory of free space, the acoustic potential energy was expressed in quadratic form of normal velocity on coupling surface and ARM of coupled enclosure was redefined. Furthermore, theoretic derivation showed that ARM of coupled enclosure could be replaced simply by corresponding acoustic mode projection of enclosure when the coupling surface was discretized into equal size elements. Therefore, the ARM theory of coupled enclosure which was consistent with that of free space and convenient for application was formed. Finally, numerical calculation was performed and the results proved that the presented theory was very efficient in ARM calculation of coupled enclosure and ASAC.