A resonance frequency of an oscillator (probe) subjected to a free vibration changes when it contacts with another material, depending on the elastic constant of the contacting material. We use a langasite crystal for the probe, which is a piezoelectric material and can be vibrated by a solenoid coil with a non-contacting way. We applied a biasing force on the probe through nodal points of the vibration to press the material. Then we can isolate the probe from any other mechanical contacts except for the material. Thereby, one-point acoustic contact occurs only with the material and we can determine the local elastic constant, quantitatively. We applied this technique to an SiC_f/Ti composite material as an example.