Detectability of the deletion of a tone from a tone-plus-noise background

The deletion of a 1,000-Hz tone from a tone-plus-noise background is much harder for humans to detect than the insertion of the same tone into a background of noise. A mathematically ideal O, oblivious to the context in which an observation interval occurs, performs equally well under conditions of insertion and deletion. Human listeners, not oblivious to context, produced the function d_s = 0.036 E/N_o under deletion; the slope of this linear function is no more than half that of the typical slope of the comparable insertion function. The underlying reasons for the superiority of detection of insertion to that of deletion remain unclear.