In immersion testing, near field effects of a transducer may be eliminated by:

• A. Increasing transducer frequency
• B. Using a larger diameter transducer
• C. Using an appropriate water path
• D. Using a focused transducer

Answer: (C)

Near-field effects come from the beam still being in its developing, nonuniform state right in front of the transducer. In immersion testing, the distance the transducer is from the test surface—the water path—controls whether you’re looking at echoes from the near field or from a more uniform far-field region. By choosing an appropriate water path, you position the inspection region so the signal is primarily in the far field, where the beam is steadier and reflections are easier to interpret, effectively eliminating the problematic near-field distortions.

Increasing frequency or using a larger diameter transducer tends to extend the near-field region rather than remove it, and while a focused transducer concentrates energy, it doesn’t automatically remove near-field effects across the inspection depth.