On the use of energy based metrics in active structural acoustic control

Abstract

Given the benefits of using acoustic energy density for active noise control in enclosures, it was hypothesized that active structural acoustic control (ASAC) might also benefit by incorporating an energy-based structural error quantity. Power flow, or structural intensity, and structural energy density were studied for use in an ASAC system. Power flow was found to be unsuitable for general-purpose use in this application. Its minimization properties are such that for a general case, it may be impossible to predict structural or acoustic response based on a minimization of power flow amplitude in a two-dimensional setting. Additionally, sensor placement is complicated by the large changes in power flow field orientation caused by a small mass loading for a lightweight structure. Structural energy density was found to be a suitable error metric, and provides a slight improvement over velocity-based ASAC in enclosed spaces. A genetic algorithm was used to study structural energy density sensor placement on a simply supported plate. At modal frequencies, optimum control was achieved by placing the sensor at antinodes. The placement of the control force was found to be less critical, but showed a slight tendency towards locations remote from the disturbance force with low velocity cross-derivative.

Active Structural Acoustic Control of Clamped Flat Plates Using a Weighted Sum of Spatial Gradients

“…Terms in (7) are scaled by a factor of / when the derivative is taken as shown by (10). Likewise, (8) and (9) are scaled by factors of / and / as shown by (10) and (11). These scaling factors are responsible for the difference in magnitudes of the terms.…”

“…This allowed for the first radiation mode to be targeted specifically as well as several other higher but significantly radiating modes. Structural energy methods have also been investigated but with limited success [9].…”