Engine noise insulation?

[Foster Nordic]

Hi all
I have a Nordic Tug 37 - wonderful long term cruising vessel. But With the Cummins 6BTA directly beneath the pilot house there is quite a lot of engine noise, even at 7-8 knot cruising speed. Has anyone investigate ways to further insulate noise from the engine room? I’d love to hear any suggestions or experience.

 

[ktdtx]

http://https://www.practical-sailor.com/blog/reducing-boat-noise


I think the most common and straight forward way would be installing energy absorbing or reflecting sheets under the floor. They are available at many marine supply stores.

 

[Keysdisease]

There are several things to investigate regarding noise reduction.

How "tight" is your engine space?
Is there existing insulation? If so what kind?
Are there hatches with no gaskets?
Bulkhead and overhead penetrations for cables and plumbing
How does combustion air get to your Cummins?

I have seen cases where an owner does an outstanding job of insulating the engine space overhead and not measure a significant reduction...because the combustion air trunk came above deck and was built into cabin sides with vents outboard, and that was the dominant noise path.

Get a Db meter for your phone and listen and look around. If you have wood floors and hatches to the ER, use masking tape to seal the hatch and take before/after measurements.

If you have existing insulation, if it's just "foam" without a vinyl noise barrier consider replacement as foam alone does not reduce noise transmission by any large degree.

Before spending a lot of money and effort try and determine where the dominant noise sources are, and treat the easy and inexpensive ones first. Hatch gaskets for example can reduce noise by 5 to 10 Db without a high cost.

Good noise reduction is often the sum of several treatments, not just one solution. As usual, the devil is in the details

$00.02

 

[Comodave]

I typically use Soundown products for noise insulation. As said above find out what you have for insulation now. Look for noise leaks and plug them up. It can be quite a bit of effort but will payoff. I have used Soundown underlayment under the carpet in previous boats with good success if you have carpet. I used the 2 pound per square foot underlayment. It is probably the easiest to install since you just lay it on the deck and then carpet over it. But if you don’t have carpet then you will have to work in the engine room installing the insulation. With a diesel you want mass in the insulation so I use the 2 pound per square foot that has a loaded vinyl in the middle. I get the PSA and also use the pin type hangers and epoxy them to the overhead.

 

[Captain Doug]

I have a 2003 Nordic Tug with the same power. From the factory it was heavily soundproofed and my meter shows 65-72 db at 1400 rpm (8 kts). Air boxes are very large and hatches are all tight to open. Pilothouse is teak/Holley with throw rug over hatches.
I don’t think there is room for more insulation and if there were it would have to be cut around wiring and devices, so not continuous.
Was your factory insulation removed maybe?

 

[Comodave]

Maybe lay out thick area rugs??? Easy and they may help absorb some of the noise.

 

[Flatswing]

My boat is way quieter at 1300-1400 rpm (7 knots +/-) than it is at our former cruising speed of 7.5-8 knots (1700 rpm). Most days cruising, the extra 30-40 minutes reaching the next anchorage isn’t an issue but we arrive more relaxed (plus save a gal./ hr in fuel).

 

[C lectric]

If the engine hatch, and I believe it is , is in the middle of the saloon/pilot house then have a good hard look at that hatch. I've only been aboard one and that was a number of years ago. If there are gaps when laid down then a huge amount of noise can get through.
THe fibberglass hatch itself may vibrate so cover the engine hatch surface with the SOundown foam.

My boat , the engine is right below the saloon which is where we pilot from. We used to have to yell at each other to communicate. No more. The boat is not quiet but one heck of a lot better as we can converse now without yelling.

All I did was cover the three hatches with Soundown loaded sound absorbing foam ensuring that the gaps were closed.
Of course I did the rest of the saloon floor over time but doing those engine hatches first was a huge improvement.

Look around for any other openings to the E.R. and close them with pieces of foam, spray foam [don't go nuts}

And be aware of noisy rpms. You may not have that but avoid them if you do.

 

[CharlieO.]

What Decibels have you people measured at cruise from the helm? Just curious because I downloaded a Db meter on my phone to check ours just out of my own curiousity. Our lower helm is about 2 feet forward of and just above our Lehman.

 

[OldDan1943]

Remember, you trap the noise, you trap the heat.

 

[Comodave]

Remember, you trap the noise, you trap the heat.

Not necessarily, you can have good insulation and also good ventilation.

 

[Turtle Blues]

Cost analysis of installing most professional sound products below deck end up being about 1K$ per decibel reduction. Easier and cheaper is good quality sound absorbing padding and wall to wall carpeting.

 

[joezzz]

quieting engine noise

I have delivered a number of Nordic tugs and they are bit noisy.

There are several solutions. I personally own a 37' Lord Nelson tug, with a 4DT3 (4 cyl. version of your engine)
1. Insulate the engine room, everywhere
2. Use a softer engine mount..........cuts down on the vibration thru the engine stringers............but there is a catch.
softer mounts means engine can move around a bit more, thus leading to

vibration due to shaft/engine misalignment.
3. There is a solution. Add an Aquadrive isolator between the shaft and engine.


Its a bit of project. But if you plan on doing extending cruising it will be well worth the time and money spent.

 

[CarlF]

As mentioned, Sounddown is the best place for boat sound control. They are also very helpful on the phone. Give them a call.

To control engine noise you need:
1) Seal all gaps coming into the salon. Even a small opening will defeat all the work you do.
2) Use a combination of foam and dense noise blocking layers. The foam isolates vibration and the mass layer blocks the sound transmission.

https://soundown.com/marine-noise-control/

 

[wkearney99]

If the engine hatch, and I believe it is , is in the middle of the saloon/pilot house then have a good hard look at that hatch.

This applies for most other boats as well. My EB47 has a hatch in the salon that has foam molding forming a gasket under the hatch. It's compressed enough over the years to no longer be useful. Don't assume that just because the fastening method is tight that the opening is as sealed as it should be. Because when the two on mine are dogged tight you can still hear a noise difference when standing on it or not.

My 'to do' list has had replacing that on it for longer than I'd care to admit.

 

[ronobrien]

There was a fairly detailed post on TF not too long ago about steps one owner took to address the issue you are bringing up. I think we'd all be interested in how you make out. Good luck.

 

[kapnd]

High density underlayment under the I/O carpet helped quiet my motor somewhat, did not measure results, but conversation has improved.
Motor is hard mounted, so I don’t expect huge sound reduction to happen unless I go to soft mounts, and possibly a driveshaft/thrust bearing arrangement.
Vibration is particularly bad at idle.
The great thing about the hard mounts is that the engine to shaft alignment is spot on, and does not change when the motor torques up.

 

[Mako]

Since I'm not the type of guy to spend $1000 per dB, I bought 2lb MLV on Amazon and my marine adhesive at Home Depot. Knocked my sound level at the helm down to 75dB. Still too high for me but tons better than before.

Someone had recommended to me previously with my Jimmies to silence the air intake, and the valve cover, both big sources of noise. Is there anything you can do to your Cummins to reduce the noise levels escaping it? Perhaps some temporary sound blankets surrounding it, sorta like a poor-man's generator box.

 

[OldDan1943]

For me, nothing is more comforting than the ‘noise’ of a well running diesel.
Plus, when the engine noise goes away or changes, time to go into the ER

 

[Duvie]

Dan, agree with you 100%. Removed the old tired sound insulation from my last two boats. Never operated from the flybridge as you cannot hear enough engine detail.

Often run the engine at a particular speed based on the “note” I feel like listening too.

 

[rslifkin]

There's a big difference between being able to hear what the engines are doing and having no sound insulation where you get sick of the noise after a few hours. On most boats, unless you're on a flybridge far away from the engines and also have quiet exhausts, you'll have a hard time reducing the engine noise to a level so quiet you can't hear what they're doing.

 

[Mako]

Have you guys ever spent a week at sea with sound levels in the PH in the 80’s? It causes hearing loss and noise fatigue and is potentially dangerous.

There’s a limit.