| 摘要 |
<p>This invention relates to the non-destructive testing of wooden poles and like objects to sort out those which are sound from those whose characteristics, when tested, indicate that they may have deteriorated. A mechanical signal of constant amplitude and at a chosen constant frequency is injected into the pole at a first position. The mechanical vibratory energy present at a listening point on the other side of the pole is converted into an electrical output. The electrical output is passed through two filters connected in parallel and having mutually exclusive pass bands; the first filter passing a frequency or range of frequencies found empirically to be virtually unaffected by the condition of the pole and the second filter passing a frequency or range of frequencies whose amplitude is found empirically to be significantly affected by the condition of the pole. The levels of the electrical outputs of the two filters are compared with one another. A read-out value obtained from the comparison is provided which signifies with its magnitude whether the pole should be examined more thoroughly. The invention also comprises an apparatus for use in carrying out the process.</p> |
