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Old 05-09-2016, 07:19 PM   #61
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Originally Posted by caltexflanc View Post
Anyone here realize that noise levels double every 3db, thus lowering tolerance by half? Just a little fyi...
Here's a chart I'd seen as to perception.

Perceptions of Increases in Decibel Level:

Imperceptible Change 1dB
Barely Perceptible Change 3dB
Clearly Noticeable Change 5dB
About Twice as Loud 10dB
About Four Times as Loud 20dB


I then found this explanation that explains your 3dB and what appeared a difference in charts, but is not.

Ratio doubling means:
− a power level of +3 dB, or a sound intensity level of +3 dB
− an electric voltage level of +6 dB, or a sound pressure level of +6 dB
− a loudness level of about +10 dB
−10 dB more SPL means 10 times increase in amplifier (electric) power.


So 3 dB doubles the sound intensity, even if it takes 10 dB to double the loudness with which we hear it.

Your point is certainly very valid that we might think of going from 70 to 77 at being minimal and only a 10% increase, but it's a huge increase.

I personally do not like yelling or being yelled to. I'm soft speaking and prefer to talk that way. I can be loud but reserve that for singing. The moment I feel like I must yell to converse on a boat is when I'm going to find a way to reduce the sound.
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Old 05-09-2016, 07:32 PM   #62
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You want to reduce the sound? Move away! Sound follows the inverse square law.
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Old 05-09-2016, 07:40 PM   #63
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You want to reduce the sound? Move away! Sound follows the inverse square law.
Wifey B: You'll just hear the sounds of splash followed by gurgle gurgle.
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Old 05-09-2016, 07:45 PM   #64
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Thanks for this post and insight into your positive experience with the Flemming 55 (great boat). While I'm not 100% positive I believe the soundproofing enhancement on the new Helmsman 38E models will use similar materials and construction process to achieve a superior level of comfort. I'm glade to hear you view point and excited to see the level of improvement on our boat compared to earlier models which I already thought very quiet boats.

John T.
Helmsman 38E - Under Construction
It will be interesting to hear your real world POV after delivery. Was just on a Helmsman 38 and was a bit surprised the engine is directly under the PH (Guess I hadn't studied the deck layout well?). On the Fleming the engines are under the salon, and there are two huge fuel tanks between the engine room and the rest of the boat going forward. In the Fleming brochure they also tout the Aquadrive system as another means of quieting the boat.

I'm not saying the Helmsman will be louder, we all know about the tech advances in materials, plus the new engines being quieter, I'm just curious to know how it goes!

All the best.
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Old 05-09-2016, 09:15 PM   #65
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Anyone here realize that noise levels double every 3db, thus lowering tolerance by half? Just a little fyi...
Somehow the entire dB scale is less than intuitive...
I studied math (years ago!) and it still seems foreign to me...
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Old 05-09-2016, 09:33 PM   #66
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Anyone here realize that noise levels double every 3db, thus lowering tolerance by half? Just a little fyi...
Kinda reminds me of the Richter Scale.

Rich·ter scale
ˈriktər ˌskāl/
a numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations. The more destructive earthquakes typically have magnitudes between about 5.5 and 8.9; the scale is logarithmic and a difference of one represents an approximate thirtyfold difference in magnitude.


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Old 05-09-2016, 09:49 PM   #67
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Not sure I would call it noise!

My ears are 20 foot off the water on the FB. I usually run the Lugger 174hp engines at 1800 (WOT is 2400, continuous duty is 2200). They are way below me in the well-insulated ER.

Any noise is from the exhaust. Since I usually have the Glendenning syncs on I would say it is more like a distant twin engine airplane sound rather than noise. We can certainly have a normal conversation on the FB or PH.
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Old 05-09-2016, 10:16 PM   #68
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On the bridge... We love to listen to the mellow back and forth revolution gentle-hum of our engines while they are in near perfect syncro at just under hull speed!
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Old 05-09-2016, 11:28 PM   #69
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The Cummins video, it sounds like they showed it at 3 different RPM's. What they were I don't know. Take a ride in a new 6.7 Dodge pu, and you will instantly notice the lower noise levels. Same holds true for the marine QSB.
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Old 05-10-2016, 12:31 AM   #70
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She purrs like a kitten. Rrrrrrrrrr!


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Old 05-10-2016, 02:24 AM   #71
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Quote:
Originally Posted by Insequent View Post
You want to reduce the sound? Move away! Sound follows the inverse square law.
Interesting all this. I'd like to thank whoever posted re the dB measuring apps, because I downloaded one called 'dB Meter Pro', and am having a lot of fun with it. Interestingly, background noise in what one would call a quite quiet environment is still 35-40dB most times. That surprised me a bit. This inverse square law thing is a bit weird really...
Looking forward to testing inside our boat at cruise speed next time we go out.
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Old 05-10-2016, 08:43 AM   #72
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We have about 5" of insulation in the engine room including perforated aluminum sheathing so the sound gets absorbed into the insulation. The insulation package is 2-3" of fire retardant spray foam then 1/2" plywood, 2" of rock wool insulation, then perforated aluminum sheathing. The plywood was installed on the walls only so I could screw fixtures to the walls anywhere I wanted.

In the wheel house with the doors and windows closed, we see between 50-55 decibel @ 1600 RPM. I'm dry exhaust, and have a flapper for a rain cap on the exhaust, and when idling, the flapper slapping will get the decibel spiking at 55. At idle, the exhaust flapper is sort of loud with it's steady metallic clap, but I kind of like it as it reminds me of my old tractor I no longer own.

The boat's extremely quiet.

I've not checked the roof with the dry exhaust outlet nor the cabin where the engine room door is and am curious as to what readings I'll see. At cruising RPM, when in the engine room, ear plugs probably should be worn.

While building the boat, we had chartered an older 42 Grand Banks in Florida for a week vacation. At cruising speed on that boat, it was almost unbearable being in the salon. The noise was bad, but almost as bad were the rattles and vibrations. The complaints from the wife asking if our boat was going to be this loud sent me down the path of how to knock down sound in a boat. The folks at Sound down gave me lots of insight as to what an engine room sound proofing system needs.

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Old 05-10-2016, 09:11 AM   #73
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The complaints from the wife asking if our boat was going to be this loud sent me down the path of how to knock down sound in a boat. The folks at Sound down gave me lots of insight as to what an engine room sound proofing system needs.

Conall
Hi Conall

Irrespective of boat sound (but, good going to keep wife happy!) I would love to see better photo of your boat in avatar. Looks real nice. I love the bow. Appears that baby does well for handling seas.

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Old 05-10-2016, 10:06 AM   #74
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Connal, thanks for the tip on Sound down.

Did you use any of their products in the engine room? Curious how that went, "sounds" good.

Their products look similar to stuff I've used by E.A.R. Their stuff was used to line sub hulls for US Navy. I learned enough to be dangerous with sound abatement from those guys.
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Old 05-10-2016, 10:18 AM   #75
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OK, if you guys think logSPL app is cool, go google "spectrum analyzer for iPad".

A spectrum analyzer shows you what frequencies things are vibrating at and how "loud" they are. That means you don't have to guess on the noise source, you can tell if it's RPM related, prop speed related, or a fundamental of what ever the forcing function is.

Last time I used one of these it cost $28K and lived on a roll around cart! Now it's an app for a phone or tablet! These things have become the Star Trek Tricorder for boats, amazing.
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Old 05-10-2016, 10:41 AM   #76
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Originally Posted by Conall63 View Post
In the wheel house with the doors and windows closed, we see between 50-55 decibel @ 1600 RPM. I'm dry exhaust, and have a flapper for a rain cap on the exhaust, and when idling, the flapper slapping will get the decibel spiking at 55. At idle, the exhaust flapper is sort of loud with it's steady metallic clap, but I kind of like it as it reminds me of my old tractor I no longer own.

The boat's extremely quiet.
That is an understatement!
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Old 05-10-2016, 11:31 AM   #77
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Last time I used one of these it cost $28K and lived on a roll around cart! Now it's an app for a phone or tablet! These things have become the Star Trek Tricorder for boats, amazing.
Phone apps still amaze me. Seems like every day something new and it's free or $2.99 to do something that cost thousands before. Look back and old science fiction movies sometime. We watched one recently. What was science fiction in the movie had now been surpassed.
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Old 05-10-2016, 12:11 PM   #78
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Phone apps still amaze me. Seems like every day something new and it's free or $2.99 to do something that cost thousands before. Look back and old science fiction movies sometime. We watched one recently. What was science fiction in the movie had now been surpassed.
Teleportation is coming. First it will be small material objects. Eventually it will be larger objects. Then, it will be living things. And, then... it will become used for human beings. Talk about high tech!

In 50's / 60's Grumman Engineering silently performed underground studies on "anti-gravity". I learned in the late 60's; by having repeat conversations with a relatively close source to the project: Gravity and molecular "gluem" (that's what they called it back them) are kissing cousins. Once gravity consuming an object can be successfully and stably removed the molecules can be disassociated and transported via electric current to be re-associated. There were "things" lost during the experiments. From what I understood some of the findings sent shock waves throughout the participating scientists and engineers ranks. Top secret level commitment on this project did not allow the engineer to provide me with deep discussion on many of the facts that were uncovered. That project was suddenly closed down. I imagine that after those discoveries some 50 + years ago that there is still silent research ongoing... somewhere. Knowing the human mind - a breakthrough will some year arrive.

If teleportation of matter actually becomes available... talk about a technological game changer!!! GEEEEZZZZ!!!

Beam Me Up - Scotty!!!
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Old 05-10-2016, 12:59 PM   #79
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Normal conversation . . . another reason to love a flybridge.

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Old 05-10-2016, 01:12 PM   #80
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Normal conversation . . . another reason to love a flybridge.

I.E. ...

Talken with Ez through gentle fly-bridge breeze! Ya gotta luv it!!
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