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Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing, UT

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

Preparatory Notes for ASNT NDT Level III Examination - Ultrasonic Testing

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Q1-20 Two plate yield different back-wall reflections in pulse-echo testing<br />

(18dB) with their only apparent difference being in the second material void<br />

content. The plate are both 3” thick. What is the effective change in acoustic<br />

attenuation between the first and second plate?<br />

Answer: Sound path – 2 x thickness = 6” Attenuation = 18dB/6” = 3dB/in.<br />

Comment:<br />

The answer could be confused if the pulse-echo testing, 2-ways path length<br />

was not considered, arriving with the incorrect answer of 6dB/in

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