What is a significant limitation of contact testing in ultrasonic applications?

A significant limitation of contact testing in ultrasonic applications is that it may produce inconsistent results on rough surfaces. Contact testing relies on direct contact between the transducer and the test material, requiring effective transfer of ultrasonic signals. If the surface is rough, it can create gaps between the transducer and the material, leading to air pockets that disrupt the transmission of sound waves. This can result in scattering and attenuation of the ultrasound, which then makes it challenging to obtain accurate and repeatable measurements.

In contrast, smoother surfaces facilitate better contact and sound transmission, thus providing more reliable results. Additionally, other options address different aspects of ultrasonic testing limitations, but they do not specifically highlight the impact of surface condition on the consistency and reliability of contact testing results like the selected choice does.