Abstract: The acoustical effects in the stalls in the average theatres are often not satisfactory. This is primarily results of unfavourable time and intensity distribution of the short-delay reflected sounds which arrive after the direct sound.
In this experiment, delayed sounds produced artificially were made use of to imitate nine different reflected sounds （20-110ms）, combined into several delayed sound combinations. Subjective evaluations by paired comparisons were made in open air among these combinations. Two musical and one speech programs recorded in open air were used as the sound signals.