Enigma loggers are deployed at positions either side of the suspected leak position (2 logger mode) or with a third logger to improve accuracy of leak position (three logger mode). They are deployed typically on valves or hydrants, during normal working hours. They may be programmed for either daytime or night-time operation. The loggers record the actual leak sound. When retrieved the leak sound is transferred to the host software where it is processed to display the leak position between loggers.