Achieving effective Active Noise Reduction in a transformer station in a residential area
A transformer station owned by Westland Infra Netbeheer in the Dutch town of Poeldijk has recently been fitted with an Active Noise Reduction (ANR) system. This makes use of a technology which is also known as anti-noise. There were plans to build new houses close to the transformer station so the transformer station had to meet certain noise requirements. Merford was asked to find a way to reduce the noise pollution levels to a maximum of 40 dB, at a distance of 21 metres on the side of the station where the houses were to be built. An ANR solution was developed to be installed in the transformer station so the sound emissions were reduced to the required levels.
Transformer station in Poeldijk, the Netherlands
When it was known that homes were to be built close to the transformer station in Poeldijk, it became necessary to reduce the sound levels of the transformer. This was due to legal requirements for the prevention of noise pollution in residential areas. Although the transformer house was fitted with grills for natural ventilation, there was no space to fit these ventilation grills with silencers on the inside. Also, it was not possible to develop other solutions outside the transformer station. This project was the ideal opportunity to introduce a system incorporating Active Noise Reduction.
Noise reduction through ANR
The ANR system consists of a double speaker, fitted within a frame tuned to the frequency to be reduced – in this case the 100 Hz and 200 Hz frequency ranges. Using this method, a large area can be covered with ANR systems. A microphone measures the incoming sound level, the ANR system processes this and transmits a counter-noise signal. This reduces the noise in this case by 6 dB in the 100 Hz frequency range and 13 dB in the 200 Hz frequency range. These reductions eliminate the tonal noise as well as reducing the overall dB(A) value by 4.3 dB(A).