A simplified model is developed for describing the free and forced oscillations of the quadrupole mode of a liquid drop freely suspended in a liquid host. The decay rate of the free oscillations and the phase‐frequency relation for the forced oscillations are derived and compared with previous theories. A parameter, interfacial viscosity, is included as an example to demonstrate the versatility of this simplified model. The application of this model in determining the interfacial tension between two liquids is discussed. The experimental technique and some results for different liquids are briefly reviewed.