Steerable parametric loudspeaker with preprocessing methods

The emerging applications of the parametric loudspeaker, such as 3D audio playback systems, require both controllable directivity and high fidelity at the audible frequency (a.k.a. the difference frequency). Although phased array techniques have been applied and proven adequate to steer the mainlobe of a parametric loudspeaker, and preprocessing methods have been studied to reduce the harmonic distortions, there has been no published work on the effectiveness of the combination of a beamsteering method and a preprocessing method for the wideband steerable sound beam system. This paper thus aims to investigate in this specific area. Firstly, the relation between the phases of the primary waves and the difference frequency wave is explored to prove the feasibility of generating a wideband sound beam from a steerable parametric loudspeaker with preprocessing methods. Secondly, based on the derived relation, a beamsteering structure is proposed. Lastly, spatial performances of a steerable parametric loudspeaker are presented in this paper using two preprocessing methods, i.e. the double sideband modulation (DSBAM) method and the square root modulation (SRAM) method, respectively.