improving acoustic insulation

No superyacht owner wants to lie in a full width suite and hear the rumble of the variablespeed generator set, or the gurgle of the sewerage plant. Instead, the living quarters of a floating palace should be whisper quiet – well, usually. There are certain owners who want to host an offshore rave but these are relatively rare.

Most metal hulls, and some composite ones (including carbon fibre) can resonate easily, so insulation basically involves interposing a soundproof layer between the resonator and the interior décor.

The remedies include everything from dense acoustic barriers as a laminate within plywood sheets, to special sound-absorbing paints that are applied to pipes and flat metal surfaces.

Great efforts are also made to quieten the machinery exhaust with large mufflers, along with acoustic barriers and baffles throughout air intakes and ventilation shafts.

At the recent Cannes boat show, for example, Turkish builders Numarine announced a 34m motoryacht that is claimed to be ‘quieter than a library’ when under way. “The only thing that you can’t totally soundproof is flat sheets of glass,” said Numarine’s technical director “They can still resonate slightly, and modern superyachts have a lot of glass! We can’t do a lot about external water noise, either, but we can do a lot to suppress noise transmission through a hull. This has given us a big yacht returning just 34dB in the saloon under way, whereas the usual requirement is around 50dB.”

acoustic barrier plywood is used behind a decorative veneer. note how the dark, barrier layer is near the surface for maximum effect

other types are more for thermal insulation, but will deaden sound too. they’re typified by a thick layer of closed cell foam – in this case blue, by the italian supplier Bellotti