MEASUREMENT OF THE VISCOSITY OF LIQUIDS BY NEAR-FIELD ACOUSTICS

We have studied the relationship between the acoustic properties of a near-field acoustic sensor and the properties of a liquid. An acoustic stepped horn is driven by two piezoelectric elements. The generated a coustic waves cause the solid horn to resonate and an acoustic load at the tip modifies these oscillation modes. This leads to a change in e lectric impedance at the piezoelectric elements. This sensitivity to a coustic load allows a study of semi-infinite liquids. We found a relat ion between the resonance frequency and the liquid density and a relat ion between the electric impedance and the viscosity.