Testing for leaks under tile floor - GIF

Testing for leaks under tile floor.

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Previously:

Detecting water leaks using sound - GIF
Ceiling leak catcher - photo
Gas leak explosion - GIF
Juice factory tank leak - GIF
Leaking bathroom tile - GIF
Water fountain with leak detection dye - GIF

I believe that is actually a microphone that is listening for the sound of the leak instead of a moisture meter.