Listening and learning: non-invasive monitoring of mineral processing equipment

The use of acoustic emmissions for process diagnostics probably dates from as far back as 6500 BC, when potters realised that they could rely on the cracking noise of clay vessels cooling in the kiln to assess the quality of their products. The famous 'tin cry' phenomenon, produced by mechanical twinning of pure tin during plastic deformation, was known to ancient alchemists from the beginning of the Bronze Age and gave rise to what is probably the first documented observation of acoustic emissions, as 'harsh sound' and 'cracking noise', in an eighth century Arabian alchemy textbook, 'The Sum of Perfect Magistery'.