In our previous research the polyisoprene – nanostructured carbon composite (PNCC) has been approved as perspective smart material to be used as pressure sensing material for low pressure. The main advantage of PNCC is hyperelastic flexibility compared to conventional piezo-ceramic pressure sensors as well as outstanding sensitivity for small (<1 bar) pressures. The PNCC is elaborated by incorporating highly structured particles of good conductor (Printex XE2 carbon black) and necessary curing ingredients into raw elastomer matrix (Thick Pale Creppe natural polyisoprene) and vulcanizing afterwards. One can find in literature that the final electric properties of composite are greatly dependant on mixing method used. In our work we use ultrasound source as an alternate method to disperse nanostructured filler. The roll mixed, mechanically mixed in solution and ultrasound mixed in solution PNCC samples were made. Their critical electrical percolation concentrations were determined and critical indexes were calculated for all types of PNCCs using linear trendlines on log-log plots. The piezoresistive behavior of such composites was evaluated and compared.