By Dr Matt Harmon, VP of Engineering, Tribosonics

Industrial monitoring systems are built for harsh environments, but occasionally, nature provides an unexpected stress test!

During a recent field deployment, one of our acoustoSENSE installations experienced a tornado. High winds, intense rainfall and structural vibration created exactly the kind of chaotic acoustic environment that would typically trigger a whole raft of false positives.

What followed reinforced two critical design choices behind acoustoSENSE: high-frequency sensing and high-resolution data capture.

The hidden challenge: false positives

Pressure relief device (PRD) monitoring systems must solve a difficult problem: detect genuine, short-duration release events without being triggered by unrelated environmental noise.

Industrial sites are saturated with low-frequency energy from rotating equipment, structural vibration, impact noise and weather. Lower-frequency sound travels further and is more likely to activate sensors positioned some distance away.

During extreme weather, this effect intensifies. Wind loading excites pipework and support structures. Rainfall produces repeated mechanical impacts. Debris and pressure fluctuations introduce further noise.

Traditionally, this can result in false positives; alerts triggered not by a valve lifting, but by the environment itself.

Why frequency is important

acoustoSENSE operates in a high- frequency band aligned with the physics of turbulent PRD discharge.

When a PRD lifts, high-pressure fluid escaping through a relatively small opening, becomes turbulent. Molecular interactions and surface friction generate high-frequency acoustic emissions that propagate through the valve body and pipework.

By monitoring in the 100–500 kHz range, much of the low-frequency background noise common on industrial sites is naturally filtered at source. Higher-frequency signals attenuate more rapidly and are more localised, reducing the influence of distant vibration and environmental interference.

But high frequency is only part of the solution.

Environmental noise does not always stay neatly confined to lower bands. Under extreme conditions, this energy can extend upward into a higher-frequency range. When that happens, simple threshold-based systems may still trigger.

The role of high-resolution data

This is where data granularity becomes crucial.

Rather than reducing each detected event to a single amplitude metric, acoustoSENSE preserves and transmits detailed characteristics of the acoustic waveform.

Environmental impacts, even severe ones such as tornados, tend to produce short, irregular or impulsive signatures that differ from turbulent discharge.

By capturing higher-resolution event data, the system can distinguish between:

• Turbulent flow from a lifting valve
• Transient mechanical or environmental disturbances

In other words, frequency selection filters most unwanted noise at source and the resolution of the data allows for filtering what remains, ensuring only genuine releases are notified.

What happened during the tornado

During the tornado event, the system remained fully operational and despite intense wind and weather-induced vibration, it did not produce a cascade of false PRD alerts.

This went beyond simply surviving harsh conditions. It demonstrated that:

• Background environmental noise was largely excluded through high-frequency monitoring.
• Further differentiation of the waveform characteristics at high frequency is automatically calculated.
• Only events consistent with real PRD release behaviour are classified as such.

The extreme conditions effectively provided a live-field validation of both the frequency strategy and the data resolution strategy working together.

What this means for PRD monitoring

For PRD monitoring, accuracy is not optional. False positives consume engineering time, undermine trust in monitoring data and can complicate compliance reporting. At the same time, missed events are unacceptable.

The combination of:

• High-frequency monitoring
• Continuous, always-on sensing
• Granular event characterisation

creates a layered defence against false alarms while preserving sensitivity to genuine releases.

The tornado was an extreme case, but industrial sites experience smaller-scale acoustic disturbances every day: storms, vibration, impact, rotating equipment and transient mechanical activity.

Therefore reliable PRD monitoring, is not achieved through thresholds alone. It requires aligning with the physics of turbulent release and capturing enough detail to distinguish real events from environmental noise.

Learn more about acoustoSENSE

 

* Image credit: Weather Radar from 14th February 2026, NEXRAD National Reflectivity Mosaic, data provided by NOAA/NWS