| 摘要 |
A method of inspecting a workpiece (1) comprises: a) injecting a pulse of acoustic energy into the workpiece, the pulse having a finite bandwidth with a centre frequency; and b) monitoring over time the receipt of signals resulting from transmission of the pulse in the workpiece. Steps a) and b) are repeated at least once, the centre frequency of the pulse being different in each step a); and the information obtained in the step b) is compared to identify one or both of those types of signals which are received at substantially the same time at each frequency, and those types whose times vary with frequency. Information about the workpiece (1) is determined from one or more of the signals identified in step d). |
