Production noise in the audible range is effectively filtered out by the ultrasound camera and does not interfere with leak detection—therefore, reliable measurements can be taken even in noisy facilities. In many production environments, there is also little or no interfering ultrasonic noise; in which case leak detection can be performed immediately. In some areas, however, stronger sources of ultrasonic interference are present. For these more challenging situations, there are proven methods for better managing the interference and still reliably locating leaks. This guide shows how.
Many production noises fall within the audible range and have only a limited impact on ultrasonic leak detection. Even in plant areas with moderate sources of ultrasonic interference, medium-sized and larger compressed air leaks can often be reliably detected during operation—especially from short to medium measurement distances.
However, it is important to note that not every visible ultrasonic source is automatically a leak. In automated systems, pneumatic vents, valves, machine movements, friction processes, or reflections can also generate ultrasonic signals. The decisive factor is whether these sources of interference fall within the same frequency window as the leak signal being sought. An ultrasound camera locates sound sources within a defined frequency range and makes suspicious hotspots visible. The evaluation is then performed in the context of the system—for example, based on pressurized components, cycle timing, viewing angle, frequency spectrum, measurement distance, and display stability.
In compressed air systems, medium and large leaks in particular generally offer the greatest potential for savings. At the same time, they represent strong ultrasonic sources and should usually be repaired first. In technical gas and vacuum applications, however, even smaller leaks can be highly significant—for example, for quality, process, or safety reasons. When detecting very small leaks in acoustically challenging environments, physical factors such as sound attenuation, reflections, and the signal-to-noise ratio at the measurement site play a greater role.
To fully leverage the potential of ultrasonic camera technology, we recommend a tailored measurement strategy, the right choice of equipment, and a reliable interpretation of the measurement results. We would be happy to advise you on which leak detector is best suited for your production environment and support you with online or on-site training to ensure optimal use.
Practical example from an automated system: Multiple hotspots can arise due to process movements, pneumatic systems, or reflections. Relevant leaks must be assigned to pressurized components.
The better the signal-to-noise ratio in the relevant frequency window, the more effectively and at greater distances leaks can be detected. In a quiet ultrasonic environment, therefore, physically much smaller leaks can be detected than in areas with strong sources of interference.
Verify the hotspot on the pressurized component
A hotspot should first be verified on the system. A genuine leak occurs at a pressurized point, such as a screw connection, coupling, pipe, fitting, gasket, or valve. If, on the other hand, a hotspot is indicated on a wall, sheet metal, protective screen, or the floor, it may be a reflection.
Physical Background: Ultrasound is strongly reflected off hard surfaces. The camera may then appear to indicate a source at the reflective surface, even though the actual sound source is located elsewhere.
Action: Change the viewing angle and measure again. A genuine leak remains consistently visible on the component. A reflection moves, changes position, or disappears.
Reduce the measurement distance
If the leak signal is too weak compared to the background ultrasound, the distance to the suspected source should be reduced, for example, to about 1 m or even closer at close range.
Physical Background: The sound pressure from a source decreases with increasing distance. As the distance to the leak decreases, the sound pressure level measured at the microphone array increases. At the same time, more distant sources of interference become relatively less significant. This improves the signal-to-noise ratio.
Action: Move closer to the pressurized component and scan the area again. This is often crucial, especially in the case of weak leaks.
Check the Frequency Spectrum and Shift the Frequency Window
The FFT display helps identify dominant interference frequencies in the measurement environment. If strong ultrasonic components are present within the currently selected frequency window, the display may become erratic or mask a leakage signal.
Physical Background: Leaks typically generate broadband ultrasound. Interference sources, on the other hand, may dominate specific frequency ranges. If the active frequency window is shifted so that strong interference components lie outside the window, the separation between the leak and the interference improves.
Action: Shift the frequency window to a range with less interference. In practice, it is often advisable to test higher frequency ranges. It should be noted, however, that higher ultrasonic frequencies are more strongly attenuated by air. For greater distances, lower or mid-range frequencies may therefore be advantageous.
Adjusting Sensitivity, Threshold, and Dynamic Range
With the UltraCam LD 500/510, users can adjust the acoustic sensitivity and threshold to suit the environment. The threshold determines the sound pressure level at which an acoustic event is displayed as a visible hotspot. If the threshold is increased or the sensitivity is reduced, weak background signals are suppressed. The ultrasonic image appears cleaner and is easier to interpret. The LeakCam 600 further assists the user by automatically adjusting the dynamic range of the ultrasonic image. In Auto mode, the system analyzes the level distribution in the ultrasound image and adjusts the display to produce the clearest possible image. In Manual mode, the user can adjust the threshold themselves to suit local conditions.
Physical Background: Reducing sensitivity or setting a higher threshold does not improve the actual leak signal; rather, it suppresses weaker signals. This makes the display more stable, but very small or distant leaks may no longer be visible under certain circumstances.
Action: In case of strong interference, increase the threshold or reduce the sensitivity. When searching for microleaks, quiet the environment, move closer to the source, select a clean frequency window, and increase the sensitivity again accordingly.
Eliminate dominant sound sources first
Significant leaks, open vent lines, ultrasonic baths, fans, blowers, or other dominant sources can mask weaker leaks.
Physical Background: When multiple ultrasonic sources are present in the measuring range, the strongest source dominates the display. As a result, smaller leaks may disappear from the ultrasonic image or cannot be reliably evaluated.
Action: First mark, document, repair, or temporarily shut down dominant sources. Then scan the area again. Weaker leaks often become visible only after the strongest sources have been removed.
Monitor the process status
In automated systems, many ultrasonic sources occur only intermittently. Examples include pneumatic cycling, valves, cylinders, screwdriving processes, presses, grinding, drilling, milling, or cycled venting.
Physical Background: A true leak usually generates a relatively stable, reproducible ultrasonic signal as long as pressure is applied. Process-related sources, on the other hand, often occur in sync with movements, cycles, or processing steps.
Action: Check whether the hotspot is permanently visible or occurs only during a specific process step. If necessary, repeat the measurement during a downtime phase or non-production period.
Temporarily Increase System Pressure
If permitted by the process, the system pressure can be temporarily increased to the maximum permissible operating pressure.
Physical Background: As the differential pressure increases, the volume flow escaping from a leak generally increases. This causes the generated ultrasonic level to rise, making the leak easier to detect.
Action: Increase the pressure only within the permissible operating limits and then measure again. This measure is particularly helpful for small leaks or those that are barely detectable.
Perform the measurement during quiet process phases
If reliable localization is not possible despite optimized settings and a reduced measurement distance, the measurement should be repeated during a quieter phase.
Physical Background: The smallest detectable leak is largely limited by the signal-to-noise ratio. The lower the background ultrasound, the weaker the leak signals that can be detected.
Action: Search for microleaks whenever possible during non-production times, downtime, or when sources of interference are turned off.
| Source of interference | How can you identify them? | Practical countermeasures |
| Pneumatic valves and cylinders | Short, pulsed ultrasonic signals. The hotspot appears periodically or shifts in sync with the motion cycle. | Monitor the process cycle, check specific connections, and, if necessary, take another measurement during a shutdown phase. |
| Blow-off nozzles and open compressed air usage | Very strong, stable, or pulsed ultrasonic source. Other leaks may disappear from the image. | If possible, temporarily shut them off or mark them as regular consumers. Then scan the area again. |
| Other strong leaks in the vicinity | A dominant leak can mask smaller sources. | Document or repair large leaks first, then measure again. |
| Conveyor belts, presses, friction points, and contact points | Broadband or pulsed ultrasonic components, often dependent on movement or contact. | Critically inspect hotspots outside pressure-bearing components, consider the process conditions, and adjust the frequency window. |
| Grinding, drilling, milling, and other friction processes | Often broadband, continuous, or pulsed ultrasonic signals caused by tool contact, chip formation, or material friction. | Perform measurements outside the machining process whenever possible, or shift the frequency window to a range with less interference |
| Electric screwdrivers and cycled tools | Short ultrasonic pulses synchronized with the screwdriving or operating cycle. | Synchronize the hotspot with tool operation and recheck when the tool is at a standstill. |
| Frequency converters, power electronics, and electric drives | Frequency-dependent or stable hotspots on electrical components, not at points under pressure. | Examine the system context, analyze the FFT, and do not automatically assume the source is a compressed air leak. |
| Electrical discharges / corona effects | Ultrasonic activity on electrical components, often unrelated to compressed air lines. | Follow safety guidelines, investigate the source based on the system context, and do not assume it is a compressed air leak. |
| Lamps, lights, and electronic ballasts | Hotspot on a light fixture or electronic component, often stationary and independent of compressed air components. | Turn off the lighting on a trial basis, if permitted, and check the frequency spectrum. |
| Ultrasonic baths and ultrasonic cleaning systems | Very strong technical ultrasonic source, often with dominant frequency components. | If possible, shut them down, increase the distance, or perform the measurement outside of operating hours. |
| Fans, blowers, and strong airflows | Broadband ultrasound caused by turbulence, bearing noise, or blade movement. | Identify the flow source, change the viewing angle, adjust the frequency window, and specifically inspect pressure-bearing components. |
| Media with high flow velocity in pipes | Hotspot on pipes, valves, orifices, or changes in cross-section, with no discernible leak point. | Take pipeline routing, fittings, and process conditions into account. Verify the actual point of escape before classifying the hotspot as a leak. |
| Sound-reflective surfaces and reflections | A hotspot appears on the floor, wall, sheet metal, cladding, protective glass, or Plexiglas. | Change the viewing angle or distance. A genuine leak remains stable at the component, while a reflection moves or disappears. |
Reliable leak detection does not depend solely on maximum instrument sensitivity, but on achieving the best possible separation between the leak signal and background noise. The most important control variables are measurement distance, angle of view, frequency window, threshold, sensitivity, process conditions, and the reduction of dominant ultrasonic sources.
A stable ultrasonic image is helpful, but should not be confused with higher physical detection performance. If sensitivity is reduced or the threshold is increased, small leaks may be masked.
For microleaks, therefore, the following applies: measure as close as possible, reduce sources of interference, select a clean frequency window, and perform the measurement in as quiet an environment as possible.
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uses 30 MEMS microphones for Calculation and visualization of the ultrasound image. The device also makes inaudible ultrasound audible.
Due to the integrated camera and the available accessories our starter kit for leak detection enables reliable leak detection as well as compressed air leakage calculation and reporting according to ISO 50001.