With the trend to sustainability and energy efficiency, buildings are being constructed that are attempting to be as ‘green’ as possible. One objective in this form of design is to provide a higher level of interior environmental quality than buildings that use conventional practices. Post Occupancy Evaluations have been carried out on 36 sustainable buildings in 11 different countries. This paper describes and analyses the users’ overall perceptions of the acoustical conditions and the noise sources (in particular noise from colleagues, from other people, and from both inside and outside sources) in these buildings. The results from these analyses showed that people rate the overall interior environment of these sustainable buildings highly. However, the acoustic aspect tended to score rather less well than some other aspects of the interior environment. A strong correlation was found between the occupants’ overall perception of noise and their perception of productivity in the workplace.