In this paper we present graphical tools and parameters search algorithms for the timbre space exploration and design of com- plex sounds generated by physical modeling synthesis. The tools are built around a sparse representation of sounds based on Gam- matone functions and provide the designer with both a graphical and an auditory insight. The auditory representation of a num- ber of reference sounds, located as landmarks in a 2D sound de- sign space, provides the designer with an effective aid to direct his search for new sounds. The sonic landmarks can either be syn- thetic sounds chosen by the user or be automatically derived by using clever parameter search and clustering algorithms. The pro- posed probabilistic method in this paper makes use of the sparse representations to model the distance between sparsely represented sounds. A subsequent optimization model minimizes those dis- tances to estimate the optimal parameters, which generate the land-mark sounds on the given auditory landscape.