State-space modeling of sound source directivity: An experimental study of the violin and the clarinet

A method is presented for simulating the free-field, frequency-dependent directivity of linear sound sources for use in real-time within geometric acoustic environments. The method, which is applied to modeling the directivity of a violin body and a clarinet air column from experimental acoustic data in this study, is based on using minimum-phase measurements to design a state-space filter, allowing the interactive simulation of a time-varying number of radiated sound wavefronts, each toward a time-varying direction. With applicability in sound synthesis and/or auralization within virtual environments, where sound sources change position and orientation dynamically, techniques are proposed for modeling and simulating directivity profiles on perceptual frequency axes with alternatives for representing directivity on a per-vibration-mode basis while incorporating relative phase terms or by reduced-order efficient representations comprising separate components for the signature resonant structure and the associated directivity on an adjustable frequency resolution.