Source directivity constitutes a fundamental acoustic property of musical instruments, describing the variation of radiated sound pressure as a function of direction. This behavior is dependent on the geometry, material properties, and excitation mechanisms of the instrument, and plays an important role in spatial sound perception. In the real world, the directional characteristics of a source contribute significantly to how sound is localized, how timbre is perceived across different listening positions, how sound is captured with different microphone techniques and placements, and how sound interacts with the surrounding environment. Yet, despite its importance, source directivity is often simplified or neglected in contemporary spatial audio rendering approaches, particularly within AR/VR/XR applications where computational constraints and system complexity frequently dictate design choices. Directivity describes the angular dependence of radiated sound pressure and constitutes a defining acoustic signature of each instrument. Acoustic directivity measurements are based on demanding and carefully controlled procedures. Typically, they are conducted in anechoic or low-reverberation environments using dense microphone arrays, and rely on excitation mechanisms, in order to improve measurement accuracy and repeatability. It should be acknowledged, however, that there exists a gap between acoustic research and its practical integration into immersive media technologies. Many current XR applications rely on simplified or generic source models, prioritizing computational efficiency and ease of implementation over acoustic accuracy. While there is a clear benefit on the use of simplified directivity approaches, such practices reduce the perceptual realism and fidelity of the reproduced sound field. This raises critical questions: To what extent does accurate directivity contribute to perceptual realism? Are approximations sufficient, and under what conditions do they compromise the experience? This workshop addresses these questions by exploring both the scientific foundations and practical implications of incorporating source directivity into AR/VR/XR systems. It is structured in three parts, offering theoretical information and practical perspectives on the role of sound source directivity in immersive audio applications. The first part discusses source directivity and its importance in sound emission, perception, and spatial realism. Emphasis will be given on recent research involving the capture and analysis of directivity patterns of the human signing voice across different music genres and traditional Greek musical instruments. Two directivity databases dedicated to this research, which are publicly available through the SONICOM Ecosystem repository (https://ecosystem.sonicom.eu/) will be also presented, along with an overview of their structure, content, and potential applications. The second part focuses on the integration of directivity data into spatial audio rendering pipelines for AR/VR/XR environments. Participants will be introduced to the latest updates of the SOFA (Spatially Oriented Format for Acoustics) conventions specifically created for storing and exchanging directivity information. In addition, the Binaural Rendering Toolbox (BRT), developed within the SONICOM project, will be presented as a practical tool that facilitates the implementation of directivity-aware rendering workflows. The third part concerns a critical discussion on the practical implications of using accurate or approximated directivity data in immersive audio applications. Drawing on results from selected case studies, the session will evaluate the perceptual and computational trade-offs involved, offering guidance on when high-precision data is necessary and when simplified models may suffice in AR/VR/XR applications.
