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Quiet

You don’t have to live with the noise

coming from your engine room

Boating is a quiet pastime, until you start the engines. Then, the type of boat you have and the size of the engines determines how noisey it gets. Some sounds, like the wind or music (totally subjective), are acceptable, other such as exhaust and engine and equipment vibration are classified as objectionable. Of course if you bought one of the new electric boats or a hybrid, then sound is not as much of an issue at all. Though, if sound is an issue, it’s no doubt emanating from the engine room. Thankfully, the technology exists that makes it possible to reduce much of that irritating conversation-stifling noise to a friendly decibel level.

Whether you have an older boat or a newer one there is usually something you can do that will reduce the sound that reaches your ears. Chris Murray, sales director at Soundown says that there isn’t a boat 60-feet or less that wouldn’t benefit from some noise control upgrades performed on its engine room, machinery isolators, and mufflers
One way of removing the living area from the rumble of the engines is to “float” the floor and walls, effectively insolating them from the vibration. This isn’t practical unless you are building new or performing a major refit. Barring either of those, you’re faced with putting as much mass and space as you can between you and the source. That means placing barrier materials on the overhead and bulkheads in the engine room as well as on the living area side. For the overhead, there is a composite acoustic barrier that has a density of two pounds per square foot. It consists of lead or PVC sheeting sandwiched between foam layers. The use of Soundown’s 18mm (.71inch) QuietCore M bulkhead instead of standard plywood of the same thickness can reduce noise transmission by up to 10dB, providing an audible reduction of 50 percent. That’s significant. Soundown’s Website (soundown.com) is quite helpful if you’re planning on updating your sound attenuation. It has suggested fixes for three different types of boats.
Vibrational energy, that which is generated by an operating engine, can be mitigated by upgrading the rubber isolation mounts for the engines, generators, or the HVAC compressors, if they are worn or just inadequate for the job. That will take care of the vibration prior to it forcing its way into the boat’s hull and supporting structure to become an irritating noise. Delta T Marine is a roll- or spray-on coating by Mascoat that insulates and reduces vibrations. Based on its sound tests, Mascoat claims it removes 50-percent of airborne structural noise. It provides thermal insulation as well.
The mufflers are another area worthy of some attention. Soundown makes what they call a WaterDrop Silencer. This can be installed as a regular dual discharge unit or as an option with an underwater exhaust. It that may not be a practical refit solution for small boats, as there are likely to be space limitations. Many variables effect exhaust system selection and performance, and while all upgrades will likely decrease noise levels there still may not be significant noise reduction between system types. “Look at all the options to reach your noise reduction goal. A good conventional system [no underwater discharge] may be the answer,” says Chris.
Noise will seek out the weakest point and exploit it. Sound is like water in that regard, wherever there’s a “leak path” the sound will find it. For instance, if there is space around hoses or hatches going through an engine room bulkhead, the noise will come through that spot regardless of how good the rest of the insulation is. Interrupting it with sound absorbing gaskets and seals can halt the noise.
Chris says, “When it comes to blocking and absorbing noise you can’t change physics.” If you want your boat to move through the water it’s going to make propulsion noises. Thankfully there is material available that allows you to combat the noise and vibration with somewhat of an equal and opposite reaction.