Dubbing is often employed in the original-language version of a sound track for technical reasons. Filmmakers routinely use it to remedy defects that arise from synchronized filming (in which the actors’ voices are recorded simultaneously with the photography). Synchronously recorded dialogue may be unclear or inaudible in a long-distance shot or because of accidental air traffic overhead, or it may simply be impossible to conceal a microphone close enough to pick up the actors’ voices intelligibly.