Noisy Cabin ? 88dba at idle

[SeaDuty]

TLDR
In the cabin above engine hatches
Started 85-88dba
~1.5k'ish later
Now at 71-73dba

Ok - putting this up here for those who want it a little bit quieter.

Not that I cared much as I always drove from the flybridge but after a recent outing my wife had mentioned something.. So...that's how it started.

At idle I was humming at 88 dba in the cabin. I had purchased a decibel meter to give myself a starting point.. This was many months ago.

What and where is the fun part. Took a while to really assess what could be changed vs removing major items and causing more problems.
Started with my engine hatches - had the old thin layer of who knows what loosely laying in there, plus a gap of where the hatches reside.
Lay on the floor of your engine room and look up - lots of daylight at least for me through the edging of the hatches.

added Soundown Sound-Stop Foam Panel with 1lb Barrier Layer - 2"
and Noise Grabber Mass Loaded Vinyl - 2 LB, 4' x 12', 48 Square Foot Roll of MLV
also purchased 3/4 boom mat w/adhesive from amazon to gap fill areas or walls that were difficult to deal with..

Cut large pieces of foam panel to fit inside the hatch and also underneath the cabin floor area where accessible. Fwd & aft of the water tank at the ceiling the little and sometimes large boxed areas.
Cut to fit the Vinyl and sort of created a gasket as the gap was ~1/4" all around the engine hatch and where they touch when closed. Used stainless staples with a air nailer to secure the vinyl.
My cuts in the Vinyl could be better and straighter may clean up later.
Leftover pieces were used in the compartments - under the couch / kitchen area to soundproof where I was unable to access. Directly above the engines was not possible so I proofed from the cabin area at the floor used vinyl with foam and sometimes vinyl again.. Don't use the soundproof green ****, doesn't dry - thought it was a caulking sealant - more like a forever wet adhesive(lesson learned).

I also added inline silencers to the exhaust systems (Hardin stainless exhaust silencers 4" x 5"L) Small modifications there, nothing to difficult.

Foam and Vinyl were the most effective at reducing sound , the silencers cut another 4-5dba from the back deck area and 2-3dba in the cabin.

Looked at adding mufflers but was not going to be cost effective at this time without removing fuel tanks - maybe another time.

The port cabin is next - still loud af in there

Hope this helps someone thinking about.

 

[OldDan1943]

A question for clarification, what is your idle RPM?

 

[SeaDuty]

OldDan1943

They idle about 750rpm +/-

 

[OldDan1943]

Any change in DB level if you raise it up to 800 850?

 

[SeaDuty]

They go up for certain

I only wrote down idle and 1500 rpm

cabin - start
idle dba85-88 / 1500 dba92+
didn't take measurements outside or dock at the beginning

foam-vinyl install 750rpm / 1500rpm
cabin 72.5 / 77.5
dock 83.5 / 92
deck 81 / 89

silencer 750rpm / 1500rpm
Foam-vinyl installed already
cabin 71 / 78
dock 80 / 87
deck 77 / 84

 

[OldDan1943]

And the new DB rating are sill too much sleep in the cabin?

 

[Keysdisease]

Nicely done. I did something similar to the overhead and hatches o the engine space, and in addition I used the Soundown Carpet Underlay 2 different ways. I installed it conventionally under the carpeting, and then a cut piece under a area rug that fit over the row of hatches that run down the middle of the salon. The rug and the underlay acted as a gasket of sorts to seal around the 6 hatches. The underlay was cut smaller than the rug and the foam cut away from the vinyl for 2" to create a smooth transition

Worked great

 

[OldDan1943]

Food for though:
Let’s just say, you were able to muffle the sound to near nothing, you might not hear a change in the the ambient noise and therefore, no diagnosing a problem before it gets worse.

 

[OldDan1943]

I have heard some say they cannot sleep in the aft cabin while underway.
Maybe they can consider it “while noise”? I really dont know. My berth is forward. I have heard some say, they find it difficult to sleep in the fwd cabin because of the wave noise, while underway.
Nothing more comfortable than the sound of a well running diesel. When it stops, then it is time to worry. LOL

 

[Pete Meisinger]

Not exactly rocket science but do-able for anyone. The trick is getting started, it can be messy. Especially getting rid of that old black foam stuff.

pete

 

[Keysdisease]

Food for though:
Let’s just say, you were able to muffle the sound to near nothing, you might not hear a change in the the ambient noise and therefore, no diagnosing a problem before it gets worse.

Dan, that level of quiet would only be attained if the vessel operator was deaf. 78dB is plenty of sound to hear something unusual w the engine. Without any treatments 92 dB is above OSHA workplace limits.

"With noise, OSHA's permissible exposure limit (PEL) is 90 dBA for all workers for an 8 hour day."

The typical goal for a salon is to be able to have a conversation comfortably without raising your voice or straining to hear, mid 70's at cruise for trawler sized boats is quite acceptable. At this level you are still hearing plenty of mechanical noise from the engine.

Even with the magic "no noise at all drive" wind an water noise at 8 knots is probably in the mid to high 60dB range.

0 The softest sound a person can hear with normal hearing
10 normal breathing
20 whispering at 5 feet
30 soft whisper
50 rainfall
60 normal conversation
95-100 lawnmower
110 shouting in ear
120 thunder

There are free dB meter apps for cell phones that are pretty accurate.

 

[OldDan1943]

So I’m wrong? Hmmm, first time today, I can live with that.
(Daymn, I need hearing aids.)

Comparing the Db level of rain on the ground, to rain on a tin roof. Big difference. LOL

 

[Marco Flamingo]

There are free dB meter apps for cell phones that are pretty accurate.

That's what I started out with. 78db at idle wasn't good enough. I don't really care what the noise level is at idle. But underway, I want to just talk softly. I started out with the "big sheet" idea, thinking that mass loaded vinyl covering the floor and inside the cabinetry would do the trick. Only took it down to 76db, a noticiable change, but I had to lift up sheets to access the engine room. Clunky solution. When lifting them, I noticed that the noise was coming from around the hatches. As mentioned, if you're in the engine room with the lights out and can see any cracks, that's where the sound is escaping. So I lined the hatch openings with a rubber gasket used for attaching a canopy to a pickup truck. Worked great.

I then took a foam gun into the ER and sealed up all the uneccessary penetrations. Prior owners had cut holes for electrical, for plumbing, for unknown reasons. Even screw holes could be seen and sealed. I found places like where the plumbing to the galley sink (two 1/2 inch plastic pipes) went through a 2 inch hole. Because the undersink cabinetry has louvered doors, ER noise came up through there and into the back of the salon. Doesn't matter if there is soundproofing directly between you and the engine if there is a sneak route.

At 1500 rpm, I now measure 74db. I left the mass loaded vinyl in the cabinets (it serves as a non-skid surface), but removed it from the floor and gave it away. I still have some more foaming to do in the head. The PO cut a giant hole for the toilet plumbing that goes to the VacuFlush tank in the engine room. Noise comes through there, into the undersink cabinet, out through the louvered cabinet doors, then out through the louvered head door, up the companionway, and into the mail salon. Spray foam to the rescue. It can easily be torn out for repairs/modifications and easy to replace.

True that I can't easily diagnose the engine underway based on noise. I really can't do that from the FB, where I can't really hear my engine at all. I found out that my overheat idiot buzzer doesn't work. Expensive le$$on.

I wish that everyone who posts about engine noise abatement gets the app for their phone. Claiming a $4000 soundproofing "really, really, really made a huge difference" doesn't mean as much as saying "it cut my engine noise at 1800 rpm by 2db." The phone app allows apples to apples. Same with a phone app inclinometer. I've seen posts claiming, "we took a wake and rolled 30 degrees." If they didn't soil themselves, they didn't roll that much. A phone app keeps it real.

 

[C lectric]

Well I'm another one who doesn't use the phone much and don't b uy all the gadjets;

However, my very noisy 45 yr, we had it 35 yrs, was noisy enough tat my wife and I had to virtually yell to each other.
I bought enough SOundown 1" leaded foam to do the hatches and pay attention to the gaps. THe hatches were central in the saloon along with the lower helm station and also on top of our noisy engine.
THat 1" Soundown foam made a big difference, enough so that we could actually talk with only a slight raising of the voice.

TO be clear I did not have a cell phone at all in those days, and all those cell gadgets were simply N/A.
The only Db meters were in the multiple hundreds of dollars and for a single application
not worth it to me.

So another testimonial, the Soundown made a big difference.

 

[socalrider]

This is great - thanks SeaDuty for posting your experience & measurements. This is one of those projects that's on the list but hasn't made it to the top yet.

It'd be interesting to see a frequency spectrum before & after as well. I'd suspect the SoundDown knocks off the mid to high frequencies most effectively, which are the ones we find most irritating. The low frequency thrum of a diesel is hard to eliminate but also not objectionable to my ears.

 

[rslifkin]

This is great - thanks SeaDuty for posting your experience & measurements. This is one of those projects that's on the list but hasn't made it to the top yet.

It'd be interesting to see a frequency spectrum before & after as well. I'd suspect the SoundDown knocks off the mid to high frequencies most effectively, which are the ones we find most irritating. The low frequency thrum of a diesel is hard to eliminate but also not objectionable to my ears.

Based on the data they provide, the thicker layers of Soundown and the ones with heavier mass layers on them are more effective on low frequencies, although all versions still knock down high frequencies more. Low frequencies are at least partly about good isolation to prevent the noise from resonating through the boat. While higher frequencies are typically radiated directly off the equipment, so sound deadening and closing up gaps does a lot to reduce those.

 

[Marco Flamingo]

My decibel app has a frequency graph.

Another nice free app is a vibration meter. Pick a spot on your helm where your phone tucks in nice. Record the XYZ numbers at your cruising speed in your log. Was that clunk you heard the prop hitting a log? Put your phone back in the same spot and check out whether you have an altered vibration pattern.

For reference, I measured a recent flight in a 20 passenger plane from Honolulu to Molakai. Vibrometer recorded 5.1 and the decibel meter was 81. I want to be well below those for peaceful cruising.

I use the same phone placement spot at the helm for my free apps for decibels, inclinometer, and vibration. Sometimes I use the phone as a phone, but I find the other uses more valuable. How much more valuable? There's probably an app for that.

 

[Mako]

Claiming a $4000 soundproofing "really, really, really made a huge difference" doesn't mean as much as saying "it cut my engine noise at 1800 rpm by 2db." The phone app allows apples to apples.

True, and spoken like an engineer.

Speaking about outboards, I posted a year ago about applying 2lb MLV to the cowling of my 2-stroke. Cut sound at the helm from about 95db to 75db. But that wasn’t good enough and still gave me a headache on long hauls.

 

[Keysdisease]

It'd be interesting to see a frequency spectrum before & after as well. I'd suspect the SoundDown knocks off the mid to high frequencies most effectively, which are the ones we find most irritating. The low frequency thrum of a diesel is hard to eliminate but also not objectionable to my ears.

Excellent observations, spot on. High frequency is easy and requires little mass to reduce. You can test how much reduction you might get from a gasket treatment just by using masking tape to seal the seams. A measurement before and after will usually show most if not all the high frequency like turbo whine reduced if not gone.

The lower the frequency the more mass you need. In Soundown literature they recommend 1lb product for Gas powered vessels and 2lb product for diesel, because the mechanical and exhaust noise from diesel is a lower frequency.

When in traffic and you hear loud music with a strong bass line, sometimes it can shake your rearview mirror. But you don't hear singing or guitar sounds. The high and mid range are stopped by the laminated (decoupled) glass in the car but the low just blasts right through.

As described by Marco a quiet boat is the sum of several treatments and attention to detail. We treated the salon and were very happy with the reduction, then we took 3 steps down into the galley and heard significant noise coming from the lower galley cabinets. This was from the bulkhead penetrations for plumbing and wire chases. Easy fix.

Another useful, effective and very inexpensive treatment is to fabricate a "curtain" to reduce noise travelling through the bilge. In our Mainship the bilge is open between the inboard stringers and maybe 10" up from the bilge to the bottom of the forward engine room bulkhead. I cut some 1lb Mass Loaded Vinyl cut to fit tight from the bulkhead along the stringers and touching the bilge deck, and then slit vertically to allow water to flow. I made a second curtain and cut the slits offset from the 1st curtain. This reduced the noise coming up through the deck in the galley and forward cabin.

The low hanging fruit is gaskets and sealing the little leaks like bulkhead penetrations. Combustion air paths are a major source of noise as many boats have hull vents that are common with salon side panels.

Mass Loaded Vinyl (MLV) is relatively inexpensive and your best value all around noise treatment.

 

[Dwk]

Keydisease “I installed it conventionally under the carpeting, and then a cut piece under an area rug that fit over the row of hatches that run down the middle of the salon. “
Does this carpet underpayment come in various widths? We also have a runner down the salon with no sound reducing material only a PIA mat to help hold runner in place. I have added Soundown 2” material to the 6 engine hatchs (what a difference) and would like to add the carpet underlay to the runner.

 

[Keysdisease]

Does this carpet underpayment come in various widths? We also have a runner down the salon with no sound reducing material only a PIA mat to help hold runner in place. I have added Soundown 2” material to the 6 engine hatchs (what a difference) and would like to add the carpet underlay to the runner.

All the Soundown Carpet underlays come 54" wide and Soundown cuts to length. A razor knife cuts it easily. I suggest the 1lb as the 2lb does not lend itself to rolling up or flipping back for ER access.

I used the 1/2" 1lb, and trimming the foam back from the MLV worked great to make transitions. It's also available in 1/4", but you lose the plush feel.

Once I had an exhaust leak, and the print of the hatches was clearly outlined on the bottom of the underlay demonstrating leakage.

 

[Dwk]

Thanks for the response. I’m certain this will help with db level plus the runner will most likely stay in place and not roam like what we are using under carpet runner.
What material did you use for the bilge? Any pictures?

 

[Keysdisease]

Thanks for the response. I’m certain this will help with db level plus the runner will most likely stay in place and not roam like what we are using under carpet runner.
What material did you use for the bilge? Any pictures?

The underlay goes foam side down, so it stay put pretty good. It's also heavy, that's what stops the noise, mass. That helps it stay in place as well.

https://soundown.com/architecture/carpet-underlayment/

The "curtain" I described is made from MLV, the same black rubber like sheet in the carpet underlay and insulation with a barrier. Mass Loaded Vinyl is impervious to water and oil and fuel resistant so the materiel lends itself to this application.

Soundown sells MLV, its available through many sources including online, Lowes and Home Depot.

 

[Comodave]

In a previous boat we used the 2 pound underlayment under the carpet in the salon. The engine room was too difficult to get insulation on the overhead so I went with the underlayment. Worked very well and was easy to install. The carpet guy laid it before he installed the carpet. Only problem was it came in a 400 pound roll. I had the shipping company lay it on the ground so I could cut it into manageable pieces. But I blew my knee out when I was climbing into the bed of the truck…

 

[Keysdisease]

In a previous boat we used the 2 pound underlayment under the carpet in the salon.

Tell him what it feels like to step on

 

[Comodave]

It fellt like a fairly good carpet pad.

 

[Arc]

I’m at 68db at 2000 rpm and gen running. QSB engines start out quiet. 2” SD and a decent carpet. Finding those sound leaks really help. Go around with your DB meter and hunt them down

 

[SeaDuty]

cool app

after reading these was able to download a DBA app on the phone..

I guess my standalone DBA meter will go back in the garage with all the other stuff. May save someone $20 in their next project.

may have to look at redoing the carpet as noted above and chase the penetrations with my new phone app..

thanks for the input

 

[Mako]

Good move. Also be aware of vibrations. Loose brackets and even wires slapping can all cause noise.