Which of the following is a disadvantage of ultrasound testing related to surface roughness?

• A. Surface of part must be accessible
• B. Surface roughness is problematic
• C. Experience required
• D. Couplant required

Answer: (B)

Ultrasound testing relies on a smooth, well-coupled surface to send and receive ultrasonic energy cleanly. When the surface roughness is high, the incident wave is scattered in many directions instead of reflecting coherently back to the transducer. This weakens the received signal, increases noise, and distorts echoes from features or flaws, making it harder to interpret results and potentially hide defects. That specific issue—surface roughness interfering with reliable ultrasonic signals—is why this is a disadvantage. The other items are general UT requirements (accessible surface, needed experience, and a couplant) and aren’t specifically caused by roughness.