][<en asked:
 > How often do you tap on an element of an old building to hear it's sound? <
 
 Regularly. I find though that it's important to tap on a timber with a wooden mallet rather than a metal hammer. They communicate and tell you lot's of things.
 
If the timber has been invaded by fungus or insects it looses much of of its "voice" and responds softly and desponedndly. When it it is still sound it rings with a clear tone that sounds "healthy". If it is overloaded it's tone is harsh and short or "strained" vs long and resonant. If it is cracked or broken it sounds incomplete as in the tone is unfinished.
 
These tonal qualities can be used to locate the extent of infestation, the source of excess loading or the point of fracture by walking the timber and comparing the sounds as you go.
 
Remember to watch where you're stepping while your sounding.
 
Lesson learned the hard way.
 
Rudy
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