Abstract
This paper demonstrates visualization of the radiated acoustic pressures from a complex structure by using the Helmholtz Equation Least Squares (HELS) method (Wang and Wu, 1997; Wu and Wang, 1998; Wu and Yu, 1998). The structure under consideration has the same geometry and dimensions as those of a real, full-size passenger vehicle front end. Random noises generated by a high-fidelity loudspeaker installed inside the vehicle buck are measured at certain distances away from the vehicle surface. These measured signals are taken as the input to a computer model based on the HELS method. Experiments are conducted inside a 12’ by 12’ by 6.5’ walk-in size, fully anechoic chamber at the Acoustics, Vibration and Noise Control Laboratory of Wayne State University. The reconstructed acoustic pressures on the vehicle buck surface and in the field are compared with the measured data at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the vehicle buck surface. Results show that good agreements can be obtained with relatively few expansion functions in the low-to-mid frequency range. The accuracy of reconstruction, however, decreases with the increase of the excitation frequency and measurement distance as expected. Nevertheless, the HELS method is shown to be relatively insensitive to the complexities of a vibrating structure, which may make it potentially a viable noise diagnostic tool for engineers.
