A sound system design/simulation system includes background noise to provide more realistic sound renderings of the designed space and more accurate quality measures of the design space. The background noise may be provided as a library in the design system that allows the user to select a background noise profile. The user may also provide a recording of a background noise from the built space or from a similar space. The design system converts the recorded background noise to a background noise profile and adds the profile to the library of background noise profiles. The user can select a background noise profile and associate the profile with a specified space. The user can adjust the noise level of the background noise and the design system automatically updates one or more quality measures in response to the change in background noise level.