Abstract: A method of determining the presence and location of leaks in a pipeline (2) comprising inserting a leak location device capable of detecting and recording the occurrence of noise into the flow of fluid (1) within the pipeline (2); allowing the leak location device to travel through the pipeline (2) with the fluid flow; causing the leak location device to detect and record noise in the fluid; and causing the leak location device to record the time at which noise is detected. Generally the leak location device is retrieved from the pipeline (2) downstream to its insertion point.