Quiet on the Cheap
You don’t have to spend a lot of money to lower the noise level on your boat.
What do you suppose is the problem I’m asked for advice on most often? How to make a boat faster? Nope. Burn less fuel? Negative. The question I hear most is How do I make a boat quieter? While at first this may be surprising, when you think of it, it makes perfect sense. An owner may become acclimated to a substandard cruising speed or an above-average fuel bill, but a boat that’s loud will drive everyone crazy. What fun is it to be out on the water if you have to yell every time you want to be heard?
One solution is obvious: Call in an acoustical expert. There are plenty of contractors who will come to your boat, take precise measurements in various locations, and formulate an amelioration plan that will make life aboard significantly more peaceful. Likewise, there are companies selling advanced acoustical insulation materials, along with detailed installation instructions so that you can either have them installed or, if you’re relatively handy, install them yourself.
The trouble with both options is they cost money, often a lot of money. Many boaters who complain about noise issues own older boats that were built without access to the sound-deadening materials and expertise that’s available to modern boatbuilders, and it may not be practical to pour money into these vessels that may never be recouped. And some of us are just on a budget.
This column is about neither those experts nor those materials. It’s about how you can quiet your boat on the cheap. Now we all know that nothing much comes free, and that applies here. Don’t expect monumental changes in sound levels if you’re going to go economy class. But you can make things incrementally quieter often by doing just a little work. Just how much quieter may surprise you.
The first step is to understand the difference between sound and noise. Noise is basically sound you don’t like—one man’s Pavarotti is another man’s Kanye West. But it’s not all subjective. There are certain sounds that are universally despised by the human ear—like nails on a blackboard. Likewise when sound reaches a certain level (measured in decibels) it becomes uncomfortable for most people. Conversational speech is around 65 decibels, the level of discomfort is 120 decibels, and the level of pain is 130.
Sound levels are what you should be concerned about when you buy a boat; when you already own one and want to quiet it down, you need to focus on the physical nature of sound. In simplest terms, sound is vibration that excites our eardrums and activates our auditory nerves. Of course something has to vibrate and that something can be a solid, a liquid, or air. Regardless of the medium, if you prevent one vibrating object from causing another object to vibrate, you interrupt the transmission of sound.
You need to focus on the transmission of vibration through air and solids. Each demands a specific strategy. It’s relatively easy to stop air from transmitting vibration: an airtight seal around the area the sound is being produced in will do the trick. Take your engine room, the largest source of sound in a powerboat, other than teenagers. Your engines need fresh air for combustion, so some sound will always escape through the vents. But any other passages leading from the ER should be sealed tightly. That means doors and hatches, but also any opening in a bulkhead to allow the passage of pipe or electrical cable. Sealing such openings with caulk or dense foam will reduce the amount of sound that reaches your ears.
For this strategy to be effective, you have to seal all the passages. I was recently on a boat in which the passage from the ER to the lazarette was not tightly sealed. While the lazarette was unoccupied, the sound that entered it was retransmitted through various solid components to the rest of the boat resulting in an annoying hum at cruising speed.
And that brings us to the transmission of vibration through solids. To reiterate, if something shakes something else, sound is transmitted. The best way to stop this is to isolate the vibrating solid with a flexible material that will let it shake but not hit something else. A common example is the “poor-man’s strategy” to quiet pump noise: Mount the pump atop pieces of flexible hose and screw it to the mounting surface. It may be cheap but it works.
You can duplicate this strategy anywhere on your boat, although for larger objects hose may not suffice. The point is to use whatever you need to prevent solid contact between anything that might vibrate and the structure of your boat. Isolation really works, which is why high-end yachts actually “float” cabin soles and bulkheads on synthetic rubber. And again, the more places where you block the transmission of vibration, the quieter your boat will be.
These two sound-abatement strategies—sealing and isolation—don’t have to cost a lot of money. True, you won’t get the kind of results you will with expensive materials or consultants, but they will make a discernable difference.
Now if you could just do something about those teenagers …
This article originally appeared in the July 2015 issue of Power & Motoryacht magazine.