Methods and systems for determining the resonance frequency of a resonator byDoppler effect. An interrogating sonic beam including a carrier and one ormore resonator exciting frequencies is used to excite a resonator (20). Thecarrier frequency is modulated by the resonator~s vibrations. The receivedsignal is analyzed (38) to determine the amplitude of the Doppler shiftedsideband frequencies, and the data processed to determine resonance frequencyand/or to center the sonic beam on the sensor. Calibration of the sensor~sresonance as a function of a physical parameter in the measurement environmentallows the determination of the parameter value. The methods and system may beused to determine cardiovascular or intra-cranial pressure or pressure inother body cavities or in an industrial environment.
