Which test is used to detect internal decay by tapping the wood?

• A. Sounding
• B. Penetration
• C. Visual
• D. Abrasion

Answer: (A)

Sounding relies on tapping the wood and listening to the resulting sound. When sound wood is struck, it produces a clear, sharp ping; internal decay or voids soften the structure, giving a dull, hollow, or muted sound even if the surface looks fine. This difference helps inspectors quickly identify hidden decay in timber members, guiding where more detailed tests or repairs are needed. Penetration tests gauge how easily a probe enters the surface but don’t reliably reveal hidden decay. Visual inspection shows only what’s on the surface, and abrasion testing isn’t used for detecting internal decay. So, tapping and listening to the wood—sound testing—is the best method for detecting internal decay.