Acoustic cameras: operating principle and application
In industrial environments, acoustic cameras are becoming an effective diagnostic tool, allowing for the early detection of equipment defects and improving industrial safety.
Structurally, acoustic cameras combines three main components:
1. Microphone array (usually 100–120 MEMS microphones arranged in a specific geometry);
2. Video camera;
3. Signal processing module with specialized software. Nuton Acoustics acoustic cameras are equipped with proprietary software Aura SSV.
Operation of acoustic camera is based on methods of spatial processing of acoustic signals and includes the following stages:
1. Registration of sound
Microphone array simultaneously records sound waves from object. Due to varying distances to source, the signal arrives at each microphone with a time delay.
2. Time delay analysis
Software determines differences in arrival times of signals, which allows direction of sound source to be calculated.
Using directionality algorithms, distribution of acoustic energy in space is constructed and exact position of sound source is determined.
Results are displayed as a color-coded acoustic map overlaid on real-time video stream. Color scale represents sound pressure level from minimum to maximum within camera's field of view in a given frequency range. Color of maximum and minimum sound pressure levels is determined by selected palette (in Nuton Acoustics acoustic cameras you can choose from five types). For example, in the "Rainbow" palette, red represents loudest sound source, and blue represents quietest.
5. Frequency analysis
Additionally, an analysis is performed to determine nature of abnormal sound:
– high-frequency signals – gas leaks in pressurized systems, vacuum leaks and partial discharges;
– low frequency – mechanical faults.
In terms of functionality, an acoustic camera is similar to a thermal imager. However, while a thermal imager displays temperature, an acoustic camera visualizes sound. In other words, instead of "hot spots", it shows "acoustic anomalies", accurately indicating:
– gas and compressed air leaks;
– faulty bearings and mechanisms;
– partial electrical discharges;
– other defects that are not visually detectable.
Gas leak from connection
Bearing defect
Partial discharge in a 35 kV jumper cable
Conveyor belt roller defect
- Contactless diagnostics – without stopping or disassembling equipment
- Efficiency – instant visualization
- High accuracy of noise sources localization
- Visibility – intuitive interface in software in real-time
- Versatility of application - stems from the fact that virtually any physical process in equipment generates acoustic waves. Mechanical friction, turbulent flows, gas leaks, electrical discharges, and vibration processes inevitably generate sound vibrations over a wide frequency range (including ultrasound). This makes acoustic chambers applicable to a wide range of applications.
- Improving safety – through early detection of defects and preventing accident situations at a safe distance