Studies on performance functions for interior noise control

Analytical investigations into performance functions for interior noise control are presented. Three different performance functions for global control and one performance function for local control are developed and investigated. These performance functions are based on the squared pressure, the panel kinetic energy, and the air particle kinetic energy. As an illustration, noise control in the interior of a three-dimensional enclosure with a flexible boundary clamped along the edges is considered. Active control is realized by using lead zirconate titanate (PZT) patches as distributed actuators and interior microphones as error sensors. For tonal external disturbances, optimization analyses are carried out in the frequency domain to determine the optimal voltage inputs to the piezoelectric actuators and the optimal values of performance functions. Issues such as the number of actuators and their locations are investigated when the disturbance frequency is close to one of the following frequencies: a) resonance frequency of a symmetric or an asymmetric panel mode; b) off-resonance frequency, and c) resonance frequency of a cavity mode. The controlled responses obtained for the different performance functions are analysed by using pressure contours, zones of quiet, and modal amplitude and modal rearrangement control mechanisms. Based on the results of the numerical studies, it is determined that use of the energy-based performance function results in better pressure contours and zones of quiet inside the enclosure. The location of the actuators is found to have a significant influence on the magnitude of noise reduction. The results of the studies are relevant to interior noise control in enclosures such as rotorcraft cabins.