Sound-deadening flooring in engine room

We have metal plates over the wooden floor panels in the ER. Pretty sure reflected sound causes some of the racket we have when the engines are running.

Has anyone removed the metal plates from their ER and replaced them with rubber or some other sound-deadener?

If so, what did you use and did it make a noticeable difference in noise reduction?

No, I have not done that. I bought some flooring strips from Woodcraft made for standing long times. They are almost 1/2” thick and fairly soft. You could cut them, or something like them, to size and just lay them on the metal decking. They would be pretty slip resistant and would surely be better at sound attenuation than the metal floor. Also if you don’t like them not a lot of money wasted.

You would need a very high percentage of noise absorption material in an ER to make a noticeable reduction in noise. Floor sq ft just won't add up to very much

Thanks for the feedback.

Kd, you may be right. But there’s about 45 sq ft of metal-faced flooring down there. Interesting to see if anything less reflective of sound will make any difference.

It would be easy to test. Can you remove the metal floor panels temporarily and compare sound levels. Sound meters are affordable. There are even apps for your phone. You want to avoid standing sound waves between walls and floors and ceiling. A metal floor or tank sides would provide an excellent reflecting surface. A reduction of 3 db would cut the sound power level in half.

In my last boat I had large areas of the engine room and lazarette covered in aluminum floor panels. They looked great and were easy to keep clean. But the boat was louder than I thought it should have been. Fortunately I could close the door to the pilot house so I never addressed the noise issue.

I installed SoundDown carpet underlayment through the advice and help of Keysdisease and saw a significant drop in sound levels. The high mass vinyl now replaces lead sheets as the modern sound deadener. Personally, I love the effects.

The extra bonus is the soft feel under foot in the salon. TBH, it's softer than my carpets at home.

We put the Soundown carpet underlayment in a previous boat that had Detroits in it. It certainly helped but hang on when you go to pay for it. Mine was the 2 pound per square foot and came in a 400 pound roll. Had to have the freight company lay it on the ground in the parking lot so I could cut it into pieces so I could move it without a fork lift.

Lead sheeting or foam makes the biggest difference. I have foam under my flooring, and carpet on top over the engineroom with twin DDs. I can have have a normal conversation at full rpm.

Lepke said:

Lead sheeting or foam makes the biggest difference. I have foam under my flooring, and carpet on top over the engineroom with twin DDs. I can have have a normal conversation at full rpm.

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BINGO!!

Disadvantage, carpeting, getting the carpet cleaned plus you need a good vacuum onboard too.
In the galley area, I have a spongy rubber pad. Easier to keep clean plus softer on your feet.

OldDan1943 said:

BINGO!!

Disadvantage, carpeting, getting the carpet cleaned plus you need a good vacuum onboard too.
In the galley area, I have a spongy rubber pad. Easier to keep clean plus softer on your feet.

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I hear you on those disadvantages. My boat is almost fully carpeted, but every time I clean it I'm left thinking "this carpet needs to go". Just have to figure out what to replace it with, and what additional sound isolation to add in the process...

Angus, I had steel tread plating in my engine room with Detroits. I layed down some nice, green felt carpeting from Home Depot on it in big sections. Same stuff they sell from rolls on the big rack at the back of the store, although it was thicker than the ones I see today.

It helps with cutting down acoustic reflections, felt good when on my knees down there, looked great since I barely dripped oils or stained it, and was cheap and easy to replace in sections.

However you should crawl into your ER and look up at the overhead. Probably it's covered with the typical starch perforated tiles which are worthless. I would scrape all that garbage off and apply some ML vinyl on the overhead.

It seems like laying down rubber mat on top of the metal would do as much good as removing the metal flooring and replacing it with something else.

Since this is flooring, you are trying to stop noise from "bouncing" off the floor and transmitting into a living space - so I don't think any type of mass loaded vinyl would be an improvement over rubber placed on top of metal. MLV is great for stopping vibrations from transmitting through an object and it would be good in the overhead and under the sole of the cabin as folks have mentioned above. But I don't see the cost being worth it on the ER floor. Also, if using a roll flooring product, you can put it where you can easily reach and not worry about the other areas since anything you place down will help a little. It's not like stopping airborne noises coming into the cabin where every little gap is a way for noise to transmit into your living spaces.

I'm thinking commercial mats like these (similar stuff available on Amazon or other places).

https://www.yacht-mats.com/product/engine-room-mats/

I got some floor mats from Woodcraft. Check their web site for floor mats and look at what they have.

The best thing I ever did in the engine room (aside from 4' LED lighting in the engine room) was to put gym flooring mats. They are GREAT on the knees, sound absorbing, cheap, and easy to replace if they get overly dirty...

Pads-
https://www.amazon.com/gp/product/B01IDRWPGI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Lights-
https://www.amazon.com/gp/product/B01HBT3BVM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

angus99 said:

We have metal plates over the wooden floor panels in the ER. Pretty sure reflected sound causes some of the racket we have when the engines are running.

Has anyone removed the metal plates from their ER and replaced them with rubber or some other sound-deadener?

If so, what did you use and did it make a noticeable difference in noise reduction?

Click to expand...

We have the same setup as you, I started using this product several years ago. Helps with the sound, easy on the knees and at $25 a throwaway product when done.

https://www.amazon.com/gp/product/B00B4IHXRU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Scottwb96 said:

The best thing I ever did in the engine room (aside from 4' LED lighting in the engine room) was to put gym flooring mats. They are GREAT on the knees, sound absorbing, cheap, and easy to replace if they get overly dirty...

Pads-
https://www.amazon.com/gp/product/B01IDRWPGI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Lights-
https://www.amazon.com/gp/product/B01HBT3BVM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Click to expand...

LOL, posted my suggestion same time as you. Great minds I guess!

Has anyone used self-adhesive vibration deadening mats? The type used on car wheel wells and body panels? My ER emits as much vibration and droning as pure volume

I'm thinking of coating the engine bed subframe with this and adding the foam mentioned above elsewhere.

https://www.ebay.com.au/itm/254336446530

Sound Insulation

Soundown products are another option. The previous owner of our boat had the ER ceiling (and removable hatches) covered in Soundown insulation and perforated aluminum when he did a major refit. He also added a piece of Soundown carpet underlayment under the rug. He spent a few bucks, but it really works. You can have a normal volume conversation in the salon right over the Lehman SP135 running at 1800 rpm. Never measured the decibel level but it seems relatively quiet. Just keep the ER access hatch closed .

KapnKarl

Your description is accurate, vibration deadening. This product is typically referred to as Dyna-Mat in the automotive industry. Is is designed to dampen vibration and structure borne noise in sheet metal and other thin panels. You are correct that its proper place in an ER would be the stringers in the vicinity of where the engine mounts land, however the performance characteristics of this product will not do much for vibration on a stringer, it's made for sheet metal. The product has mass, and so it will act as a noise barrier, but there are more cost effective way to do that. It has a place on boats, but those places are limited.

"adding the foam" Foam does not stop noise and is not a noise barrier. Foam is a noise absorber, and this threads focus is on if covering deck plates with something soft will absorb enough noise to be effective in reducing reverberation and the overall noise increase caused by reflective noise off the deck plates. I responded that I didn't think there was enough sq ft of deck to add enough absorption to noticeably reduce noise in that ER.

What stops noise is mass. Lead in the old days, mass loaded vinyl nowadays. When bonded to a decoupler layer on one side and an absorption layer on the other the mass layer's performance in increased substantially. A rule of thumb is simple, more is better, and for lower frequency, more mass is better.

In traffic you hear the boom boom of loud music from a car 2 lanes over. No singing, no guitar, just bass. Car windows and gaskets stop the high and mid range, not the low frequency.

Rule of thumb, gas engines 1 lb sq ft, diesel, 2 lb sq ft because of the lower operating frequency of diesel engines.

All manufacturers of marine acoustic insulation basically manufacture very similar products as they are all bound by the same laws of physics and cost effectiveness in the marketplace.

$00.02

GoneDiving said:

Has anyone used self-adhesive vibration deadening mats? The type used on car wheel wells and body panels? My ER emits as much vibration and droning as pure volume

I'm thinking of coating the engine bed subframe with this and adding the foam mentioned above elsewhere.

https://www.ebay.com.au/itm/254336446530

Click to expand...

I've been slowly modifying to reduce noise. I bought a 20' roll of 1# mass loaded vinyl (for a 30' boat) and placed it around, including right over the length of my teak cabin flooring. Makes for some inconvenience when removing hatches and didn't make as much difference as I was hoping. I have been measuring noise with a free app called Decibel X. Because I had so much MLV, I also used it to line compartments under the dinette seats, cabinets on the floor, anything between me and the engine.

What I found was that the biggest bang for the buck was covering actual pathways between me and the engine. Over the years, modifications to the engine room had compromised the original sound proofing. Installation of a new head resulted in several large openings, including one to slide a holding tank in from the engine room to underneath the floor in the V berth. Also some new holes in the forward ER bulkhead to run hoses. These holes were underneath the sink in the head, a cabinet that had louvered doors and let sound pass right through. Closing the door to the head, even though it also has louvers, made a noticeable difference in the engine sound in the main cabin.

I also had noise coming from under the galley sink in to the main cabin. I removed some of the inside cabinets and found that a new sink and drain had resulted in some extra holes in the floor, which leads directly into the engine room. The holes looked like the a one-armed attempt with a Sawzall. The biggest ragged hole was three times larger than necessary and the original was abandoned and left open. You can see in the picture that the original floor had about two inches of fiberglass sound insulation between the cabin floor and the engine room ceiling, plus the regular sound panel on the ER ceiling.

With MLV over the floor and most of the galley cabinet base, it became more obvious where the noise was coming from. The most engine noise was coming from behind me in the galley. I stuck my phone back in there and took the picture below. Then I knew that I had a project. I had to take apart some of the cabinet, which had been done when the mess was created, but they hadn't bothered to address the issue of sound.

In doing my research, I came across site that talked about the installation of sound proofing and how covering actual pathways to the noise was the most important starting point. It gave an example where Db measurements were taken from a 4 x 8 panel with a hole in it the size of a quarter. Plugging the hole made more difference than covering the entire panel with soundproofing but leaving the hole open. Get those little sound pathways done first.

Here's a picture of the "holey" mess under my galley sink. I first stuffed the holes with rockwool, then cut MLV sheets to seal around the hose penetrations with circles cut out to match the hose diameters. Rockwool is probably not the best in case it got wet, but it is what I had. In the future, I will probably get my "professional" foam gun and seal up all of the little openings from engine room to living area. Even seemingly tight penetrations from hoses and wiring could probably benefit from a little spray foam. I've used it in the past on other projects and future modifications or repairs are simple because the spray foam can be easily torn out and redone.

Marco Flamingo said:

In the future, I will probably get my "professional" foam gun and seal up all of the little openings from engine room to living area. Even seemingly tight penetrations from hoses and wiring could probably benefit from a little spray foam.

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Thanks for this - I also have a "holey mess" from decades of projects. First step in any sound reduction project is to seal the air gaps & I've been trying to sort out how to go about this - expanding foam seems like a good quick and easy way to go, but in my experience the cans make a mess of things & the foam gun solution looks like a big step up in precision.

Thanks for all the replies. I will likely go for rubber gym mats cut to size for the reflected sound coming off the metal ER floor. Mass-loaded vinyl sounds like the gold standard for isolating the ER from spaces above and adjacent to it, but that’s a “someday” project I’ll probably do in increments.