Starting from classical absorbing boundary con- ditions (ABC), we propose a method for the sep- aration of time-dependent wave fields given mea- surements of the total wave field. The method is local in space and time, deterministic, and makes no prior assumptions on the frequency spectrum and the location of sources or physical bound- aries. By using increasingly higher order ABC, the method can be made arbitrarily accurate and is, in that sense, exact. Numerical examples il- lustrate the usefulness for source separation and echo removal.
