The research proposes the notion of AVUI (AudioVisual User Interface), a multisensorial interface combining user interaction with interrelated sound and image. In AVUI, a user interaction brings upon interrelated sonic and visual feedback. AVUI combines Human-Computer Interaction (HCI), sonification, and audio visualisation techniques, aiming to create a cognitive totality or “gestalt” in the user, where different sensorial elements reinforce the interaction. Multitouch, gestural and multimodal interaction are identified as important application fields. AVUI is not exclusively utilitarian, having an aesthetic purpose and user experience concern. The research aims to answer the following question: how can interconnected sound and image be used to create more usable, accessible, playful and engaging user interfaces for multitouch and gestural interaction?The main objectives of the research are to: increase our knowledge on how interaction can be represented by sonic and visual means; identify the successful approaches to sound visualisation that generate greater engagement; improve our understanding of how sound visualisation can allow for greater usability, and accessibility with impaired users; and identify use cases where AVUI can be preferable to the traditional GUI (Graphical User Interface).Following a practice-based and design-oriented approach, and in order to achieve knowledge regarding AVUI, a succession of artifacts will be developed: an initial prototype, two case-study applications implementing AVUI, and a software library for generic deployment of AVUI. These will be subject to user tests, evaluated based on qualitative and quantitative methods, using interviews, cognitive walkthrough, video observation, and questionnaires.The main outcomes will be: functioning systems, code base, and software library for implementing AVUI; interaction theorization of audiovisual elements in the user interface; best-practice guidelines; and outreach activities.