Voice overs in film

In our film, there is a short episode of dialogue between two male characters which appear to be detectives/policemen. We were planning on having the coversation when we just filmed them however we thought that the ambient sounds from the surrounding area would make it difficult to hear what they were saying. So instead we decided to use a vioce over, still making it sound realistic in the process though, and this will enable the viewer/audience to hear and understand the talking that is taking place.