A conjugate gradient least square based method for sound field control

Description

In sound field control, a set of control sources is used to match the pressure field generated by noise
sources but with opposite phase to reduce the total sound pressure level in a defined area commonly
referred to as dark zone. This is usually an ill-posed problem. The approach presented here employs
a subspace iterative method where the number of iterations acts as the regularization parameter and
controls unwanted side radiation, i.e. side lobes. More iterations lead to less regularization and
stronger side lobes. The number of iterations is controlled by problem-specific stopping criteria.
Simulations show the increase of lobing with increased number of iterations. The solutions are
analysed through projections on the basis provided by the source strength modes corresponding
to the right singular vector of the transfer function matrix. These projections show how higher
order pressure modes (left singular vectors) become dominant with larger number of iterations. The
method proposed here not only allows to control the energy of the side lobes but also to explicitly
apply constraints over the amplitude of the solution using an active set-type method which is crucial
to avoid non linearities in the control sources.

Period	5 Aug 2021
Event title	50th International Congress and Exposition on Noise Control Engineering
Event type	Conference
Location	Washington, United States, District of Columbia
Degree of Recognition	International