Acoustic-centric modal filter design for active noise control

Local sensing/control or global error sensing/control in structural acoustics: A comparison of two techniques influence over sound power

“…The foundation of the approach is sensing orthogonal multipole radiation patterns [11,44]. The technique is amendable to both structural and acoustic sensing [8,[47][48][49][50]. The multipole decomposition technique begins by writing the acoustic pressure radiation from a (any) source in terms of acoustic multipole radiation patterns, similar to decomposition of structural velocity distribution in terms of in vacuo mode shape functions [11].…”

“…The modal filter weights are defined by W À1 n and the measured quantities (error signals) become a M ¼ W À1 n p. In the case of vibration sensors positioned at the virtual monopole locations, the estimate of the orthogonal acoustic multipole amplitudes can be simply written in terms of the velocity measurements [8,49];…”