Fashion is primarily a visual ontology consisting of definitions, theory and methods that are based on visual language. This research revises fashion by approaching it from a different—sonic—perspective wherein sound is considered not as a negative aspect but as a potential source of a new theory and facilitator of the evolution of new methods. Sound is thus presented not as a secondary quality of designed objects, but as the main idea-generator. The research opens new avenues for design thinking with ears rather than eyes. This thesis explores clothing and fashion from the perspective of listening rather than seeing, sounding rather than showing, and is a form of rethinking and redefining fashion by starting with the the statement that dress is sound.An investigation into sonic expressions is seen as a disruptive fashion practice, and could be described as a process of ‘unlearning’—encouraging one to leave behind pre-existing knowledge of fashion expressions by focusing on something else when defining and designing processes. That something else is sonic expressions. By rethinking the dressed body as a matter of sound gestalt, this research goes beyond existing communication models in fashion design to examine sonic language, wherein foundational definitions play a central role and form the basis for the new practice. The research was designed to facilitate the exploration and design of sonic expressions.The research addresses an identified gap in knowledge through the Sonic Fashion Ontology, which constitutes new, foundational knowledge of sonic expression. The research findings challenge existing theory with new terms, definitions, methods, and tools, and show the importance of understanding fashion as a platform for new knowledge production and critical thinking, along with unlearning and rethinking preconceptions of what dress is and could be. Furthermore, the results have implications for ways of thinking in design in relation to e.g. diverse communities such as the visually impaired.