Reducing ship noise an engineering feat

Marshall Day Acoustics consultant Craig Fitzgerald on board Rio de Janiero, where he is measuring...
Marshall Day Acoustics consultant Craig Fitzgerald on board Rio de Janiero, where he is measuring noise from the boom of the wharf crane, 30m from the auxiliary engine exhaust. Photo: Brian Corson
Logistics company Maersk has spoken about the engineering exercise behind silencing a fleet of Rio Class vessels visiting Port Chalmers.

The six Rio Class Maersk ships that visit Dunedin were modified with a "silencer" over the course of a year after the low, thumping noise they emitted frustrated residents as far away as Waverley.

Maersk Fleet group manager Clyde Peres said that getting silencers transported from Europe to Singapore had been a complex exercise, and the installation was done on board the six Rio vessels while they were still at sea.

"The Maersk crew on board all six vessels were also fully invested in the project, as they clearly understood the importance of this retrofit," he said.

"We are very happy to learn that the solution works extremely well and will help improve the quality of life in the local neighbourhood of Port Chalmers."

Port Otago chief executive Kevin Winders said the power from a second generator would be required to manoeuvre the Rio vessels in and out of their wharf-side position.

"So people may still hear the old noise for about half an hour each side of the Rios’ arrivals and departures."

Marshall Day Acoustics consultant Craig Fitzgerald had been on site regularly to monitor the noise, which he said came in the shape of disproportionately high levels of low-frequency rumbling.

"Traditional absorption silencers provide good mid- and high-frequency mitigation, but have very little impact on low frequency noise," Mr Fitzgerald said.

"Instead, a specifically designed reactive silencer was installed, preventing the low-frequency noise continuing further up the exhaust duct and out into the community.

"We recommended a solution that addressed the issue at source, so seeing that solution implemented and hearing the great community feedback makes this a real success story."


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