What does a hollow sound during a tapping inspection indicate?

A hollow sound during a tapping inspection suggests the possibility of decay within the wood. When wood begins to decay, the internal structure is compromised, leading to a change in density. This results in a sound that is different from what is expected in sound, healthy wood, which tends to produce a solid, resonant sound. The hollow sound serves as an audible indicator that there may be deterioration and loss of material in critical areas, making it essential for further investigation to assess the extent of any damage and ensure the structural safety of the aircraft component.