Research in haptics is actively conducted, particularly in the identification of environmental stiffness, which includes mass (inertia), viscosity, and elasticity, collectively known as environmental impedance. One method involves fitting the motion equation based on four physical quantities-acceleration, velocity, position, and environmental reaction force-measured during contact with an environmental object. While studies widely employ this approach to identify environmental impedance, there is no unified definition for the contact method. Consequently, identified environmental impedance is optimized for the specific contact actions, lacking generalization in the obtained data. To address this, we focus on frequency components and define contact actions with multiple frequency components as optimal contact strategies. We experimentally validate and compare the generalization of environmental impedance between the proposed and conventional methods.