International audience The EU-funded 3D Tune-In (http://www.3d-tune-in.eu/) project introduces an innovative approach using 3D sound, visuals and gamification techniques to support people using hearing aid devices. In order to achieve a high level of realism and immersiveness within the 3D audio simulations, and to allow for the emulation (within the virtual environment) of hearing aid devices and of different typologies of hearing loss, a custom open-source C++ library (the 3D Tune-In Toolkit) has been developed. The 3DTI Toolkit integrates several novel functionalities for speaker and headphone-based sound spatialisation, together with generalised hearing aid and hearing loss simulators. A first version of the 3DTI Toolkit will be released with a non-commercial open-source license in Spring 2017.