Sound reflection reduction overhead

chortle

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In my pursuit to reduce unwanted noise while cruising I am going to add some Soundown material to the overhead in the pilothouse. It is amazing to me how much noise is generated by the reflection of this hard surface. I tested the concept by standing in the pilothouse and listening closely while talking, engine off, sitting at the dock. As I was talking I stepped out from under the pilothouse roof and there was quite a difference. I tested this again last week after half of the Soundown was installed in the pilothouse by talking under a section without and then with the material in place. Once again, quite easy to hear the difference. I will post some more photos of the installation once it is completed.

20140131_152059.jpg
 

Toolate

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Whats the final surface overhead?

I was going to go all out with some painted beadboard fore and aft until I thought about the noise. White pinhole headliner is the plan now. I think fabric or foam of some sort would be the best option not a solid surface. Absorb not reflect the sound.
 

chortle

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Whats the final surface overhead?

I was going to go all out with some painted beadboard fore and aft until I thought about the noise. White pinhole headliner is the plan now. I think fabric or foam of some sort would be the best option not a solid surface. Absorb not reflect the sound.
The overhead attenuation is a perforated vinyl coated polyimide foam that has some certification for resistance to burning. Link to Jamestown below.

Soundown Perforated Acoustic Headliner

It does make some difference with reflective sound. I plan to take some dB readings before and after to see if I can quantify how much.

It is stapled to the overhead, I will post some photos in the next day or two of that detail and some more once the battens have been varnished.

I used some coated plastic beadboard for an overhead that I built years ago in the forward cabin of a Dyer, it came out looking pretty good, was inexpensive and was easy to do. Sound was not an issue on that boat in the forward cabin. Photo attached.

2009-09 fwd cabin.jpg
 

Toolate

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That is the stuff. Only asked because your pic looks like 2 panels of the ceiling are shiny/hard so wasnt sure if you were changing it all or taking it away or what. Bead board looks great- was going to use PVC as well but not now.
 

chortle

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That is the stuff. Only asked because your pic looks like 2 panels of the ceiling are shiny/hard so wasnt sure if you were changing it all or taking it away or what. Bead board looks great- was going to use PVC as well but not now.
The shiny overhead panels are two places where the Soundown has not yet been installed. It is nice and shiny because I had them sand and paint the overhead before putting in the sound attenuation.
 

jojobee

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Sounddown states in its handbook that an effective way to reduce noise is to isolate the engine from the shaft by using a thrust bearing and to install cushy mounts. I believe they mention Aquadrive by name. If you would like any information on this, give me a call. We have on staff one of the pioneers in this technology. Jim has been consulting on this system for close to 30 years.
Joe
Mack Boring
I'll PM you my number
 

JB Sportfishing

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When we bought our first panels of Nidacore for redoing the deck in our Harris they came from an acoustic supply house. If they worked well for acoustic sound insulation we figured they work good as a ceiling. When we built our Northern Bay (charter boat) we used 1/4 Nidacore as a drop ceiling. It worked really well as a sound damper, cleans easy, and we were able to recess LED lights in it.
 

Toolate

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The shiny overhead panels are two places where the Soundown has not yet been installed. It is nice and shiny because I had them sand and paint the overhead before putting in the sound attenuation.

"Them" ? Can I borrow "them"? Whoever they are.
 

Fish220sr

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chortle

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Are there mold problems with the perforated soundown for the ceiling? Or just regular mold as that happens towards the second half of season?
Your observation has merit. I have been on many boats over the years with both perforated and plain vinyl covered foam headliners, both above and below decks. The perforated will certainly allow more moisture to more easily get to the foam, it will also allow it to dry out more easily. It is also more likely to be better at reducing reflected sound. The plain vinyl is certainly easier to clean. If the pilothouse were open on all four sides 24/7 then I would have chosen the plain vinyl to help reduce how often and how much of the foam gets wet or has increased moisture content. The arrangement that I have is not subject to direct spray and gets a lot of ventilation so I opted for the perforated material. I think that it will perform better at reducing reflected noise and at the same time get enough ventilation to stay dry enough to minimize any mold growth. Only time will tell if I am right or not.
 

Toolate

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Just using 3M spray adhesive to put it up?
 

chortle

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Just using 3M spray adhesive to put it up?
No adhesives, just staples into mahogany battens. Here is a detail photo of the work in progress. The battens act to provide a gap for the hardware and wiring that is on the surface of the plywood overhead. There will be varnished mahogany battens to cover the staples and the joints between the sheets of Soundown.

detail.jpg
 

chortle

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new pics of the overhead soundown install

Not quite done yet but further along. Some more detail work to do but this is the current state of the upgrade. The last two pics show a before and after during the upgrade. There are plans for some additional varnished trim and some covers for the wiper motors.

looking better.jpg

port side view.jpg

in process.jpg

nearly done.jpg
 

chortle

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dB Measurements

Borrowed a sound meter from Mast&Mallet and took some readings at the dock to put some numbers on the improvements that have been made. I took some measurements last year underway using a friends iPhone app so those are my reference point. Not very scientific but some numbers to show the progress that I can hear.

I took readings at idle, 650 rpm and at full speed, 2400 rpm, both unloaded, sitting at the dock with a wood bulkhead aft and to port and a large, two story metal building about 10 feet aft of bulkhead. There are also some one and two story metal buildings 20-30 feet to port so there is possibly some reflected sound from those sides and certainly from directly aft. I expect reduction from reflected sound out on the water but some addition from movement through the water under load so maybe a wash? Next week I plan to take some more readings underway with the same iPhone app for a more direct comparison.

Last year at full speed underway the iPhone was reading 94-95 dB and 80ish at idle so I am pretty pleased with the progress shown in the following readings:

at idle, engine hatch open: 82 dB, closed: 67 dB, 64 dB aft port quarter.
at 2400 rpm, engine hatch open: 100 dB, closed: 85 dB, 82 dB aft, 78 dB to port.

At the end of the day I have met my goal of 85 dB in the pilothouse at full speed but there is still some more room for improvement, there is no Soundown on the forward bulkhead forward of the engine and there are some areas that need to be caulked around wires and joints and some seams to be taped but I can do that over the next few weeks.

Oh, and vibration reduction, BIG difference with the new rubber isolation mounts for the engine, nothing is buzzing or walking around anymore. I am sure I got some sound reduction from them.

So, what did it cost to do this? I totaled up the material costs for the two Soundown silencers, 1.5" and 2" composite insulation foam, 1/4" perforated foam for the overhead, hoses, clamps, plywood, fir and mahogany lumber and four rubber isolation mounts for the engine: $4181. Does not include and labor costs so this is a DIY cost but the cost of a pair of good hearing aids is around $5000 and parents go through them every couple of years in a constant search for ones that work, sooooo, which do you prefer?

Some reference data from the International Maritime Organization for noise limits onboard ships:
Work spaces
Machinery spaces (continuously manned) ** 90
Machinery spaces (not continuously manned) ** 110
Machinery control rooms 75
Workshops 85
Unspecified work spaces ** 90
Navigation spaces
Navigating bridge and chartrooms 65
Listening posts, including navigating bridge
wings and windows 70
Radio rooms (with radio equipment operating
but not producing audio signals) 60
Radar rooms 65
Accommodation spaces
Cabins and hospital 60
Mess rooms 65
Recreation rooms 65
Open recreation areas 75
Offices 65
** Ear protectors should be used when the noise level is above 85 dB(A), and no individual’s daily exposure duration should exceed four hours continuously or eight hours in total.

You guys like photos so here they are.

82 dB at 650 rpm unloaded.jpg

67 dB at 650 rpm unloaded.jpg

64 dB at 650 rpm unloaded.jpg

100 dB at 2400 rpm unloaded.jpg

85 dB at 2400 rpm unloaded.jpg

82 dB at 2400 rpm at transom.jpg

78 dB at 2400 rpm port side.jpg

Soundown completed overhead.jpg
 

Toolate

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That boat is a piece of art.

Great report and congrats on the reduction. Should make for much more comfortable cruising. Really going to caulk around the wires etc? How much space/how many holes do you have?

Is this it for sound deadening or will the quest continue? I have seen some hanging soundown curtains that look like they would really deaden things. Have to be removed for service but might get you a couple more dB.
 

chortle

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Thanks for the kind comment, I hope that Joel White is pleased with my work, she does make me smile every time that I see her. There really are a several places in the engine room that could be sealed or foamed and a couple of places where I only have a piece of 3/4" ply with no Soundown.

I imagine all of the holes with wires going through them are great places for all of that sound energy to go whistling through and that is what the Soundown folks tell me, that there is a big bang for the buck with some simple caulk, spray foam and gasketing that can gain several dB.

I experienced the best $/value from $20 worth of Poron closed cell foam gasket around the lip of the hatch gutters. That is a no brainer and so I have more of that stuff to do. The Poron gasket that I used is just held on with the self adhesive that they came with and that does not last very long. It is too thick and too dense so I have ordered some more material that is wider, thinner and softer. I will remove the old stuff and install the new stuff and see how it sounds. If it sounds good I will re-attach it with contact cement and cry uncle and say done with that portion.

The front face of the engine room bulkhead is covered with lots of stuff and it will take some diligent effort to apply 2", 2# Soundown to it but that will likely reap some benefits, especially in the forward cabin. That is my lowest priority for sound reduction as it really is just a space to inhabit when the boat is stopped for extended socializing and cocktailing and sleeping but when underway it will transmit reflected noise back into the pilothouse so maybe a few more dB reduction could be realized from some detailed work and a few scraps of Soundown and some spray foam insulation. Once again, not much material cost, just attention to detail and my time, the type of stuff that can be done with a beer close at hand.

At the end of the day, in a few years when the engine dies and I replace it with a new tier III or IV much quieter engine then all of this work will still be useful.

Some recap photos, before and after kind of stuff to see where there were big holes or lack of insulation. Some of the new work done is not 100% sealed, some loose edges or places where sound can move past gaps or do a little dance to get from here to there without a direct barrier of some sort.

1a.jpg

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2a.jpg

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3a.jpg

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4a.jpg

4.jpg

big hole.jpg

stbd side fwd pnl that needs foam.jpg
 


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