This article documents the resolution of a problem encountered during the design of a semi-permanent interactive sound and video installation currently being installed at a tram station located in Dublin, Ireland. This artwork generates video and multi-channel sound output in real time, responding to changes in traffic patterns on an adjacent street. While the visuals are composed from pre-recorded content, the sound environment explores the use of site-specific sound within public urban space by sampling and processing sounds that occur naturally in and around the station. Regulations involving the artwork's volume resulted in the sound output being reduced to a level at which it was too subtle to be noticed amidst the busy activity of the station. It was therefore necessary to strengthen the artwork's aural presence without interfering with the subtleties of the site-specific sound environment. A dynamic field of sine tones and rhythmic glitches was composed to augment the more subtle sounds of the installation. This juxtaposition of site-specific sound with compositional structures associated with the popular musical genre known as microsound proved to be effective, calling attention to the mediated sound environment even at low volume levels and balancing the artwork's presence with the other functions of the site.