Measurement of the viscosity of liquids by near-field acoustics

Abstract

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 acoustic waves cause the solid horn to resonate and an acoustic load at the tip modifies these oscillation modes. This leads to a change in electric impedance at the piezoelectric elements. This sensitivity to acoustic load allows a study of semi-infinite liquids. We found a relation between the resonance frequency and the liquid density and a relation between the electric impedance and the viscosity.