Experimental Validations and Perturbation Tests of Vibro-Acoustic Reconstruction Using the Helmholtz Equation LeastSquares Method

摘要

Experimental validations of reconstructing vibro-acoustic responses of a rectangular plate subjectrnto harmonic excitations using Helmholtz equation least-squares (HELS) method are shown. Thernobjectives of this experiment are to examine the accuracy and effectiveness of HELS method forrnreconstructing vibro-acoustic responses of highly non-spherical geometry. The dimensions of thernplate were 24× 48 cm2, which was placed on soft foam to simulate free boundary conditions, andrnwas excited by a mechanical shaker. The radiated acoustic pressures were measured by an arrayrnof 63 microphones with 6 cm spacing among individual microphones in two patches. These datarnwere taken as input to the HELS codes to reconstruct the normal velocity distributions on thernplate surface and acoustic intensity distribution on a plane at 6.5 cm distance. The reconstructedrnnormal surface velocity distribution was compared with that obtained by a scanning laser and thernacoustic intensities compared with those measured by an intensity probe at the same distance andrnpoints. To gain insight into the HELS method, perturbation tests were conducted systematicallyrnin which random errors were introduced to the coordinates of microphones, microphone spacing,rnphases and signal to noise ratios in the input data. These erroneous data were used to reconstructrnthe vibro-acoustic responses and their impacts were examined. Results of these perturbation testsrnshed light on the robustness and limitations of the HELS method as a practical tool for analyzingrnnoise and vibration mechanisms in engineering applications.