| 摘要 |
1,153,238. Acoustic inspection devices. HEATH Inc. 12 Dec., 1967 [6 Oct., 1967], No. 56396/67. Heading H4D. A wooden pole is tested for internal decay by generating an impulse on one side of the pole, detecting acoustic energy with a transducer positioned on the opposite side of the pole, filtering the transducer output into two different frequency bands, and providing a meter indication of the relative energies in the two bands. As shown, the pole 10 is struck by hammer 12 at ground level and transducer 13 output is filtered into a high frequency band (1 kHz to 5À2 kHz) and a low frequency band (160 Hz to 600 Hz) for separate amplification in amplifiers 30, 30a. The amplifier outputs are applied via respective diode/capacitor smoothing circuits (in output circuit 37) to the two terminals of a difference meter. It is stated that a sound pole gives predominantly high frequencies, and the apparatus is calibrated such that a meter deflection one side of centre indicates a sound pole and a deflection the other side indicates a decayed pole. Circuit details are given. |
