Leak detection technologies attempt to identify and estimate the magnitude of pipe defects that cause inflow and infiltration or the loss of system capacity. Leak detection should be a standard practice for evaluating the baseline condition of a system – not something that is only called upon when a ratepayer reports a drop in water pressure. The simplest acoustic detection system is the listening stick. Listening sticks are typically passive devices that are composed of long metal rods with chambers or earpieces at the end. Pipelines constitute one-dimensional systems that can effectively convey acoustic signals over lengthy distances – a property that contributes significantly to the use of acoustic systems for leak detection. Correlator systems use a series of sensors distributed along a pipeline which feed audio signals into a processing device. Sensors can be set to trigger alerts under high- or low-pressure conditions, making it possible to reduce line breaks and quickly discover leaks.