Understanding the vibration response and acoustic radiation of a transient excited thin structure

Abstract

Remote sensing may be used to detect and locate acoustic sources on a structure as well as predict the geometry and material of the structure based on propagating vibration and acoustic waves. Use of remote sensing measurements to detect and locate impacts on a thin structure is desirable. For a transient excited thin structure, the coupling of the vibration waves in the structure and the acoustic waves radiating from the acoustic source can introduce difficulties with using traditional source localization techniques. To study this problem, the vibration of the structure must be modeled and understood before source localization can occur. Repeatable axisymmetric transient impact experiments are conducted by dropping a stainless-steel ball bearing on a 3.2-mm-thick aluminum plate surrounded by air on all sides. Accelerometers are utilized to verify vibration models based on a frequency-domain Green’s function as well as a finite element simulation. Wave speeds in the plate ranging between 420 and 1225 m/s are considered. A linear array of 13 microphones with 0.025 m spacing located just above the plate is used to study the resulting acoustic radiation. An acoustic-structure interaction model is developed based on these wave propagation measurements. [Sponsored by NAVSEA.]