Sonic Echo/Impulse Response tests can be performed on both concrete and wood foundations. Round steel pile foundations (pipe piles) can also be tested, but H-type piles generally cannot be tested. This is because damping of the signal energy in H-piles is often much greater than that of concrete and wood due to the large surface areas and small cross-sectional areas of these piles.
Analysis of the Sonic Echo data is performed in the time domain while analysis of the Impulse Response data is performed in the frequency domain. In both tests, the reflection of compressional waves (fastest of all wave types) from the bottom of the tested structural element or from a discontinuity such as a crack, soil intrusion, or diameter change (bulb or neck) is measured. In simple terms, the generated wave from an impulse hammer travels down in a shaft or a pile until a change in impedance is encountered, where the wave reflects back and is measured by a receiver placed next to the impact point.
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