How are wind turbine acoustics monitored?

A French acoustic office announced the commercial launch of a real-time wind turbine acoustics monitoring solution at the EWEA in November 2015. It was developed with several partners for instrumentation, communication, control, integration and funding.

This system mainly includes a probe consisting of 4 microphones and a Class 1 sonometer, installed near the wind farm. This probe communicates with a “box” that is actually the central node of the system. This box is installed in the delivery station. It acquires and processes the data, then sends instructions to the wind turbines.

This acoustics monitoring system identifies and separates the different sound sources in the wind farm environment because each noise has its own sound characteristic. It locates these sound sources and then isolates the contribution of each wind turbine to ambient noise. The system then analyses this contribution.

All the data from this type of acoustics system is cross-referenced with the instantaneous operating data of the fleet allowing for the proper control of each sound situation encountered (stopping one of the wind turbines during a failure etc.).

Once the data is analysed, the box communicates the results and operating orders of the wind turbine, to the fleet management system. The acoustics monitoring system then ensures that sound levels are allowed to meet regulatory thresholds.

Rain impacts the acoustics of a WTG

WTGs sometimes create noise pollution, and as most of the wind turbines are located near private accommodation, your asset consequently has to respect acoustic standards.

When setting up a wind power plant, an acoustic study is carried out to determine the difference of noise production between an ‘off’ and an ‘on’ plant. These noise differences are called “acoustic emergences”. This study could lead to a curtailment plan, which determinates when to slow down / stop the plant’s activity to prevent it from producing emergences.

As an acoustics pollution itself, rain positively impacts a wind turbine. Indeed, as it produces a noise, water drops reduce the acoustics emergences’ level.

Curtailment plans should therefore be adjusted for rainy situations. This is because, the harder it rains, the less acoustics emergences your WTG creates, as rain increases ambient noise.

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