Abstract: A method for testing timbers, such as railway sleepers, for disconformities or decay by inducing vibrations in the timber, for example with an impactor monitored by an accelerometer mounted on it and connected to a microprocessor and a display unit to give an indication of constant impact, detecting said vibrations by one or more transducers, amplifying and digitizing the transducer output and microprocessor-processing the digitized output to give an indication of disconformity or decay. One embodiment utilizes the comparison of the first half-cycle surface vibrations and shear vibrations. Another embodiment compares frequency domain information with a memory stored standard. The apparatus, comprising transducers, impactor, microprocessor and indicator is readily portable.