Sound Field Reproduction of Focused Virtual Sources with Symmetry Sigmoid Regularization Function

Reproduction of focused sound sources is a fundamental problem in acoustic signal processing. Based on the cylindrical harmonic expansion of higher order Ambisonics (HOA), a novel method for focused sound source reproduction is proposed. To restrict the near-field distortion caused by higher order harmonic components of focused sound sources, a Symmetry sigmoid regularization function (SSRF) is designed, which exhibits a more suitable attenuation characteristic. By using SSRF, we first give the generalized cylindrical harmonic expansion of focused sound sources. The concept of continuous loudspeaker is utilized over a circular array to generate the discrete loudspeaker driving function. Based on the wideband error analysis, the match relationship between the SSRF and the variance pair (i.e., the operating frequency and the expansion order) is established. Objective evaluation results show that the near-field distortion is eliminated significantly by the proposed method. The reproduction errors of interior/exterior sound field are evidently lower than the state-of-the-art techniques. The subjective evaluations also confirm that the proposed approach is able to achieve higher reproduction quality compared to the referenced methods.