Audio Engineering Society Convention e-Brief 406 Presented at the 144 th Convention 2018 May 23 – 26, Milan, Italy This Engineering Brief was selected on the basis of a submitted synopsis. The author is solely responsible for its presentation, and the AES takes no responsibility for the contents. All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Audio Engineering Society. SOFA Native Spatializer Plugin for Unity – Exchangeable HRTFs in Virtual Reality Claudia Jenny 1,2 , Piotr Majdak 2 , and Christoph Reuter 1 1 Musicology Institute, University of Vienna, Vienna, Austria 2 Acoustics Research Institute, Austrian Academy of Sciences, Vienna, Austria Correspondence should be addressed to Claudia Jenny (claudia.jenny@oeaw.ac.at) ABSTRACT In order to present three-dimensional virtual sound sources via headphones, head-related transfer functions (HRTFs) can be integrated in a spatialization algorithm. However, the spatial perception in binaural virtual acoustics may be limited if the applied HRTFs differ from those of the actual listener. Thus, SOFAlizer, a spatialization engine allowing to use and switch on-the-fly between listener-specific HRTFs stored in the spatially oriented format for acoustics (SOFA) was implemented for the Unity game engine. With that plugin, virtual-reality headsets can benefit from the individual HRTF-based spatial sound reproduction. 1 Introduction In order to provide a realistic audio for headphone re- production in virtual reality devices, directional fea- tures commonly described by head-related transfer functions (HRTFs; [1]) can be applied to audio sig- nals. Most game engines and virtual reality devices manufacturer already have started to use HRTFs in their audio algorithms. For instance, in Unity, the na- tive Unity Spatializer Plugin allows to filter audio sig- nals via factory-implemented HRTFs recorded from the KEMAR manikin. However, with these fixed HRTFs, proper spatial perception is not always guaranteed, as the individual HRTFs of the listeners are highly individ- ual and do not always correspond to the implemented ones. There exists a variety of other audio spatialization solutions (e.g. 3Dception, RealSpace 3D, Rapture3D, MS Spatializer, Steam Audio, Oculus Spatializer, etc.) for different platforms (DAW Win, DAW Mac, FMOD, Unity, Wwise, Unreal, etc.), however, none of them are able to process different HRTF sets and switching between them in real time in audio-visual virtual en- vironments. Hence, for research purposes, we have developed a spatialization plugin capable of the inter- changeable use of any HRTFs in audio-visual virtual environments. The challenge was to be able to process HRTFs from SOFA files (spatially oriented format for acoustics, AES69-2015 standard [2], [3]) in real time with head-tracking involved and to be able to switch from one HRTF set to another on-the-fly. For the plugin, as a software framework, the software package Unity was selected. Unity is a development system for platform-independent games or for two- or three-dimensional graphical virtual environment sim- ulations. These environments are created in C# and can be paired with various virtual reality devices such as Oculus Rift, Samsung Gear, or HTC Vive. With respect to spatial audio in Unity, the Audio Spatializer SDK provides an open interface of an implementa- tion of a spatializer. The Unity Audio Spatializer is