Which nondestructive testing method uses sound waves to determine material thickness and is suitable for aluminum ladders?

• A. Ultrasonic Testing
• B. Acoustical Testing
• C. Magnetic Particle Testing
• D. Radiographic Testing

Answer: (B)

Ultrasonic testing uses sound waves to measure thickness. A high-frequency transducer sends a pulse into the aluminum ladder; the wave travels to the far surface, reflects back, and the instrument converts the round-trip travel time into thickness using the known speed of sound in aluminum. This works well for aluminum ladders because aluminum has predictable acoustic properties and ultrasonic probes can scan through coatings to reach the back surface, giving a precise nondestructive thickness measurement. Magnetic Particle Testing detects surface or near-surface cracks in ferromagnetic materials, not thickness. Radiographic Testing images internal features and is more about flaw detection than directly measuring overall thickness. Acoustical Testing isn’t a standard method for this purpose.