a non - destructive method for characterizing a sputter target material comprises the steps of sequentially irradiating a test sample of the sputter target material with sonic energy at a plurality of positions on a surface of the sample ; detecting echoes induced by the sonic energy ; discriminating texture - related back - scattering noise from the echoes to obtain modified amplitude signals ; comparing the modified amplitude signals with said at least one calibration value to detect flaw data points and no - flaw data points ; counting the flaw data points to determine a flaw count ; counting the total flaw data points and the no - flaw data points to determine a total number of data points and calculating a cleanliness factor .