- AE signals are often analyzed by summarizing them into features (parameters) rather than storing full waveforms.
- The basis is calculating amplitude, rise time, duration, counts and energy for each signal that crosses the threshold (a hit).
- Continuous signals such as leaks are evaluated with RMS or frequency band energy.
AE monitoring data is expressed through parameters such as hits, counts and RMS. This article explains the definition of each parameter and how it is used to judge equipment condition.
Why analyze with parameters?
AE signals are sampled at rates of several hundred kHz or more, so continuously storing raw waveforms produces very large data. It is therefore common to record parameters that summarize each signal in a few numbers and to judge equipment condition from their trends.
Hit-based parameters
| Parameter | Definition | What it tells you |
|---|---|---|
| Hit | A signal that crosses the threshold and is recorded as one event | More hits per unit time indicate increased damage activity |
| Threshold | The minimum signal level counted as a hit | The line separating noise from defect signals |
| Peak amplitude | The largest signal level within a hit, usually in dB | Source strength, distance from the sensor |
| Rise time | Time from the first threshold crossing to the peak amplitude | Identifying source type, discriminating noise |
| Duration | Time from the first to the last threshold crossing | Signal size, continuity |
| Counts | Number of threshold crossings within one hit | Reflects both signal level and duration |
| Energy | Integral of the signal magnitude over the hit | Relative amount of energy released |
| Frequency features | Average frequency, peak frequency, frequency centroid, etc. | Distinguishing sources such as cracks, friction and leaks |
Continuous signal parameters
When a signal continues without interruption, as with leaks or friction, it is hard to split into hits. In that case, RMS or ASL (average signal level) — the average signal strength over a period — or the energy in specific frequency bands is used. This is why a rise in RMS is a key indicator in pipeline leak monitoring.
Tips for reading the data
- Values depend on the threshold. The same signal yields different hit counts, counts and durations at different thresholds, so comparisons require identical settings.
- Signals attenuate with distance. Amplitude and energy decrease as the distance between source and sensor increases.
- Trends matter more than absolute values. How hits and energy change over time shows equipment condition better than any single value.
- Look at several parameters together. Amplitude or counts alone can make it hard to distinguish noise.
Finding AE data hard to interpret?
Rina Solution provides a monitoring solution that covers the entire analysis process, from parameter extraction to anomaly decisions and alerts.
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