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Listen hard and you鈥檒l be able to tell when a buried water pipe has sprung a
leak, says Palmer Environmental of Gwent (GB 2361062). Its idea is to replace
stopcocks in the streets with valves housing waterproof microphones called
hydrophones. Each hydrophone is connected by cable or wireless transmitter to a
control centre that continually monitors the average sound level across the
system. If a water main springs a leak, the flow increases locally and sounds
louder. The control centre works out where the leak is by calculating how long
this noise takes to reach different hydrophones.