STEERABLE FIRST-ORDER DIFFERENTIAL LOUDSPEAKER ARRAYS WITH MONOPOLE AND DIPOLE ELEMENTS

Due to the recent trend toward miniaturization of acoustic transducers, differential loudspeaker arrays (DLA) of small size are becoming a popular approach to achieve directional sound radiation characterized by a near frequency invariant behavior. This makes DLAs suitable for broadband audio signal processing applications. So far, only arrays of omnidirectional loudspeakers have been used in the literature on DLAs. This work focuses on the design of steerable first-order DLAs characterized by a uniform linear geometry that alternates omnidirectional speakers with dipole speakers. The design is achieved by exploiting the theory of eigenbeams. First-order eigenbeam filters are formed and then combined to produce the desired steerable radiation response, making the implementation of the proposed beamformer very simple. Simulations show that the presented beamforming method is nearly frequency invariant for large frequency ranges. Moreover, we present an analysis of DLAs in terms of white noise gain and directivity index as the number of loudspeakers is varied.