Compressed air is a useful energy source but is costly to produce and prepare. A large part of the energy is lost as waste heat during compression. Around 1/3 of it is also lost as leakage during distribution and use. A heat recovery system is the solution for the waste heat and detecting the leakage area is important for the leakage. Another important consideration is knowing the amount of leakage. One problem with leakage elimination is that the pressure in the system must drop to zero, which is costly and only possible if the benefit for elimination is higher. Ultrasonic microphones are often used to detect the leak location, however, they are unreliable in quantifying the leak due to the indirect measurement and the many problems that affect the measurement, such as noise, reflection, distance, and angle to the leak. In this work, we used three different wide-band microphones and measured standard geometries of leaks that we created as circular holes in different sizes to compare these microphones and see how they perform.