A mysterious humming noise which is keeping the inhabitants of Wijk aan Zee and the surrounding area awake at night may emanate from a local transformer station owned by electricity grid company Tennet.

The humming noise has been bothering locals for some time, NH Nieuws reported, particularly at night.

“When I’m busy doing things during the day it’s not that intrusive but when it’s quiet at night and I’m in bed I do hear it,” one woman told the broadcaster.

The Tennet transformer station converts electricity generated by a North Sea wind farm and has been in use since February. Another five have been planned.

“This is what we have been afraid of,” Petri Raymakers, who had advocated against the transformer stations in a campaign called Ban the Buzz. “It is very difficult to prove where a low-frequency sound emanates from but it can seriously bother people.”

Three measurements made by the local environmental service have not been able to locate the source of the hum so far.

A Tennet spokesperson said the company had not been aware of the noise nuisance experienced in Wijk aan Zee but said they would investigate once the five transformer stations are in place by the end of December.

“If it turns out the transformer stations are making more noise than allowed with we will take measures,” he said. The results of the probe are expected in May next year.