Compressed air leakage is a significant source of energy inefficiency, leading to increased operational costs and reduced equipment performance. Although small leaks (2–10% of total compressed air consumption) are often considered acceptable in well-maintained systems, poorly maintained systems can experience much higher leakage rates. This paper outlines the development of a prototype system for detecting compressed air leaks and assessing the resulting energy losses in pneumatic systems. The prototype uses a sound detection sensor to detect noise from compressed air leaks. It is paired with a desktop user application that displays real-time data on the sequence number of measurements, detected noise levels, estimated leakage rates, and projected annual monetary losses. The system allows for quick and efficient leak detection at key points within a pneumatic system. The prototype was tested under laboratory conditions on pneumatic connectors with pre-drilled holes (1, 1.5, and 2 mm) to simulate air leakage. The results demonstrated the device’s capability to detect leaks and estimate energy losses accurately. The device provides medium-reliable detection and loss estimation in controlled environments. Future research will focus on testing the system in real industrial environments with multiple noise sources, refining the device to ensure its suitability for industrial applications. This approach aims to reduce energy waste, improve system efficiency, and lower operational costs in industrial pneumatic systems.