A method for increased accuracy of the measurement of relative phase velocity

The phase velocity may be used to detect distributed damage or to determine the elastic moduli of a material. The advent of high speed analog to digital converters makes high speed signal acquisition possible. Other research has shown that the cross-correlation can find relative delays between signals with high accuracy. This accuracy is still limited by the degree to which a signals arrival time is well defined. Dispersion of the wave results in uncertainty in the time delay associated with particular frequencies. At the same time theoretical limits exist on the resolution with which time and frequency may be known. Awareness of the existence of theoretical limitations on accuracy suggests methods which may be used to avoid these limitations. A method of processing difficult signals which considers optimal results is presented. Experimental examples illustrate the signal processing. The signal processing combines wavelet decomposition and cross-correlation to measure time delays with a high degree of accuracy.