Just-audible image displacement needs only 1 to 2 dB level change.

Evidence

At interaural level differences of ±30 dB, the extreme lateralizations of the sound image are obtained. For a restricted range of interaurallevel differences, ±1O dB, a just-audible displacement is achieved if the level difference is varied by 1 to 2 dB. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1713