Dr Sonn joined Bartlett School of Planning in 2006. He also held temporary or part-time posts at Jungbu University in South Korea, at the Korean Research Institute for Local Administration, at the Korean Appraisal Research Institute, at the Southern California Association of Governments in Department of Geography and Environment at LSE. He also had visiting posts at Institute of Policy and Management (Beijing), Chinese Academy of Science and Department of Geography at Seoul National University. He received his Ph.D. degree in urban planning from the University of California, Los Angeles and his MSc. and BSc. degrees from Seoul National University. He is active in international academia serving as editor of International Journal of Urban Sciences and editorial board members of several journals.

Dr. Sonn's research is focused on two themes in urban and regional economic development: 1) the urban and regional dimension of technological knowledge production and 2) political analysis of regional economic planning. The geographical focuses of his research are the U.S., South Korea and China. Funded projects include temporal changes of localised knowledge spillovers in the U.S. (funded by the Benjamin Stevens Fellowship of North American Association of Regional Science), the emergence of a metropolitan knowledge cluster (funded by the Leverhulme Trust), a comparative study of innovative capacities between the Seoul metropolitan area and the Southeast region (funded by the Asian Institute for Regional Innovation), creative centres as a new orthodoxy in Chinese urban development (funded by the Royal Institution of Chartered Surveyors) and Localised knowledge spillovers and regional absorptive capacity (funded by European Commission through Marie Curie Fellowship).