  Methods are proposed for modifying the reverberation characteristics of sound
fields in rooms by employing a loudspeaker with adjustable directivity,
realized with a compact spherical loudspeaker array (SLA). These methods are
based on minimization and maximization of clarity and direct-to-reverberant
sound ratio. Significant modification of reverberation is achieved by these
methods, as shown in simulation studies. The system under investigation
includes a spherical microphone array and an SLA comprising a multiple-input
multiple-output system. The robustness of these methods to system
identification errors is also investigated. Finally, reverberation and
dereverberation results are validated by a listening experiment.
