A series of studies has been made in an attempt to determine the selection of the proper independent variable that will allow for the prediction of the distribution of internal friction in mechanical vibrators of various geometries. Previous studies of cylindrical vibrating bars have indicated that the loss is a sole function of the longitudinal strain. The choice of a material for use in a generating or receiving system based upon its internal friction, can be misleading when practical geometries are used rather than the cylindrical geometry used for laboratory measurements. Impedance discontinuities caused by the selection of shape or the use of disimilar materials can lead to internal friction, in addition to that anticipated on a longitudinal-strain basis. The results of numerous measurements of losses and corresponding theoretical calculations are presented to indicate the complexity of the problem. Preliminary conclusions are presented to indicate the application of these findings.