This paper will show that increasing the probability of detection (POD), without also increasing the amount of false positives. Three 5MHz straight beam probes were used at linier distances of 22.5mm and 45mm from the transmitter. A V1 steel calibration block was used as an aid to experiment repeatability, and the 2mm notch was utilized as substitute defect. The experiments will show that the diffracted echo signal can be detected using the passive probes. © 2004 American Institute of Physics