Natural gas transmission pipelines transport large volumes of highly pressurised natural gas from storage facilities to domestic markets over a long distance. These pipelines are subjected to all kinds of deterioration mechanisms over time due to man-made damage and natural disasters which eventually would result in pipeline leakages. Leaks in gas pipelines will influence public health and lead to enormous financial losses to the industries. To prevent such situations, many researchers have looked into different techniques to detect and locate the leaks in pipelines. This paper reviews the current state of the art of leak detection systems using acoustic monitoring techniques. With increasing awareness of the quality of different leak detection systems, standards and recommended practices have been introduced to assess the performance of the systems. In addition, selected acoustic-based leak detection systems were evaluated based on the four criteria established under API RP 1130. Sensitivity and accuracy were two of the most commonly used performance measures when evaluating the leak detection systems while reliability is relatively less taken into account. Robustness was found to be the only performance metric that is rarely investigated where unforeseen circumstances such as sensors failure were not examined comprehensively.