I spent some time a the "Silent Running" booth at the Newport show last year. It's an intriguing product. Liquid (water-based) sound attenuation that you apply with a paintbrush. Have any of you guys used it, or heard anything remarkable about it?
www.silentrunning.us
Yeah, I know I should've done my homework on this months ago, but of course it completely fell off my radar until I started to think about engine reinstallation.
Silent Running
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Figment,
I have applied to the underside of the sole on my boat. It takes many coats 5-6 and you need to roll it for best results. It's expensive stuff and since I am still restoring the boat, I cannot tell you how well it really works as a sound deadener. I don't have much room for conventional material and figured if I want more sound proofing I can add the regular type stuff. Sorry I don't have much more to say at this time. Wait 1.5 years and I can let you know first hand how well it really works.
I have applied to the underside of the sole on my boat. It takes many coats 5-6 and you need to roll it for best results. It's expensive stuff and since I am still restoring the boat, I cannot tell you how well it really works as a sound deadener. I don't have much room for conventional material and figured if I want more sound proofing I can add the regular type stuff. Sorry I don't have much more to say at this time. Wait 1.5 years and I can let you know first hand how well it really works.
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Figment
- Damned Because It's All Connected
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I started rolling it on a bit today. Just a bit, though.
I chatted a while with one of the reps when I stopped in to buy the stuff. Predictably, he keeps his boat just up the river from mine, applied the product just a couple of years ago, blah blah. At some point he mentioned that, though it takes several coats to roll-on the required thickness, you can spray-on the required thickness in only two or three coats.
Those words started to ring in my ears later in the afternoon, when I was about 20 minutes into the application and had only managed to paint the little bit between the fuel tank and the starboard cockpit drain. Properly applying the product to all of those nooks and crannies on the underside of the cockpit sole was going to be a most unpleasant task, and I predict that I only have the patience to wriggle into that hole another three times, maximum.
Life's too short. I'm going to rent an airless sprayer this weekend.
I chatted a while with one of the reps when I stopped in to buy the stuff. Predictably, he keeps his boat just up the river from mine, applied the product just a couple of years ago, blah blah. At some point he mentioned that, though it takes several coats to roll-on the required thickness, you can spray-on the required thickness in only two or three coats.
Those words started to ring in my ears later in the afternoon, when I was about 20 minutes into the application and had only managed to paint the little bit between the fuel tank and the starboard cockpit drain. Properly applying the product to all of those nooks and crannies on the underside of the cockpit sole was going to be a most unpleasant task, and I predict that I only have the patience to wriggle into that hole another three times, maximum.
Life's too short. I'm going to rent an airless sprayer this weekend.
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Tony
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Hey y'all:
To qualify my post: I am head of the sound/technical arts area at my church, and have spent the last 6 years studying and learning about sound and ways to control it.
Anytime you look at controlling sound, there's always a few companies that tout spray-on or roll-on substances as a replacement for the traditional method, adding mass. It's a nice thought. They're usually cheaper and faster to apply. Depending on your application, they may be just the thing, but don't jump in just yet.
Sound is, put simply, vibrating air. Our ears interpret this as sound. The higher the energy level, the more volume we hear. The smaller the wavelength, the higher the frequency we hear. The only way to control this vibration is to find ways to reduce the energy level of the wave. Energy is a constant in the universe, so you can't just make it go away, you have to convert it into something else. This is what these folks are basing their product on, converting the energy to heat. Now, sound controlling materials work in a couple of ways: some materials oppose movement entirely, so when the wave hits the material, the material essentially pushes back and some of the energy is cancelled, reducing the magnitude of energy present. This is how lead works. Other materials sort of "absorb" some of the energy. This is how an elastic polymer works. This is also how fiberglass or rockwool panels work, except in these cases they use their porousness and depth to actually slow down the wavespeed, which increases their heat conversion efficiency, making them better than just an elastic polymer coating. There is one last consideration here, and I think this is the most important thing to consider. Generally, the material depth of a sound treatment like a spray on polymer or a sound controlling panel like I mentioned previously directly corolates (sp?) with how low in the sound spectrum it can control. I won't go into the math, I don't think the message board will let me write that much, but essentially, your material must be at least 1/4 wavelength thick for it to noticeably affect a frequency's energy level. For example, at 250 Hz, your wavelength is 4.5 ft. 1/4 WL is 1.13 feet. This means that to make a meaningful change in the energy level at this frequency, you need ~1 ft of solid dampening material such as an elestic polymer. With rockwool or fiberglass panels (note this is not fiberglass like a boat deck, more like the pink insulation in your house but denser and in a solid panel) you can go with a thinner layer due to the slowing nature of the material. If you're using a denser material, such as lead, your thickness can be even thinner due to the way the lead tends to "oppose" the wave's energy, rather than converting it to heat. As a reference, WL at 100Hz is about 11 feet. 1KHz is about 1.1 feet. 3 KHz is about 4 1/2 inches. All this to say, the spray on stuff will work ok at higher frequencies, but won't do diddly for lower freq's. If you're looking to quiet your motor, this isn't the right stuff. If you're just looking to dampen vibration noises in other materials such as your sole, this would probably work pretty well. In sound control, there is no shortcut and there is no substitute for mass. Lead sheets like Tim used are by far the best way to dampen your engine compartment. As another reference, the density of Silent Running is just about 1/10th that of lead, you'd need 10x the amount of SR to compete with Lead.
Hopefully I wrote that in an understandable way, I'll look at it tomorrow when I wake up a little more and make any corrections if they're necessary.
Edited on 08/19: I forgot to mention this about material thickness. The quick and dirty way to explain why we use mass to control sound is this: If you have a wave and it encounters a surface, that wave will try to cause that surface to vibrate at the same frequency and energy level. This is a major component of why you hear your kid's muffled stereo outside their closed bedroom, their walls are re-radiating the wave into the space on the outside of the room. Now, to use an analogy, if you drop a pebble into a puddle, you see ripples flow out from it. If you drop that same pebble onto a concrete sidewalk, you don't see any ripples...why is this? The concrete sidewalk has much more mass than the puddle. So, if you have a sound source you want to control to prevent it from coupling into another space, you want to close off all the air passages you can and put a barrier with a lot of mass between the sound source and the other space. If your barrier has enough mass, the sound source will not have enough energy in it to cause the barrier to re-radiate the sound audibly into the other space. This is why we use lead sheets in engine compartments, because there is much more energy in low frequency sound, so it takes more mass to control it. This is why your kid's stereo is muffled. The walls of his or her bedroom have enough mass to control and not re-radiate the upper frequencies in an audible fashion, but not enough to control the lower frequencies.
Keep in mind, I've done my best to condense all this into an understandable forum-sized message, so some things are oversimplified.
Hope this helps,
Tony Orchard
Vernonia, OR
To qualify my post: I am head of the sound/technical arts area at my church, and have spent the last 6 years studying and learning about sound and ways to control it.
Anytime you look at controlling sound, there's always a few companies that tout spray-on or roll-on substances as a replacement for the traditional method, adding mass. It's a nice thought. They're usually cheaper and faster to apply. Depending on your application, they may be just the thing, but don't jump in just yet.
Sound is, put simply, vibrating air. Our ears interpret this as sound. The higher the energy level, the more volume we hear. The smaller the wavelength, the higher the frequency we hear. The only way to control this vibration is to find ways to reduce the energy level of the wave. Energy is a constant in the universe, so you can't just make it go away, you have to convert it into something else. This is what these folks are basing their product on, converting the energy to heat. Now, sound controlling materials work in a couple of ways: some materials oppose movement entirely, so when the wave hits the material, the material essentially pushes back and some of the energy is cancelled, reducing the magnitude of energy present. This is how lead works. Other materials sort of "absorb" some of the energy. This is how an elastic polymer works. This is also how fiberglass or rockwool panels work, except in these cases they use their porousness and depth to actually slow down the wavespeed, which increases their heat conversion efficiency, making them better than just an elastic polymer coating. There is one last consideration here, and I think this is the most important thing to consider. Generally, the material depth of a sound treatment like a spray on polymer or a sound controlling panel like I mentioned previously directly corolates (sp?) with how low in the sound spectrum it can control. I won't go into the math, I don't think the message board will let me write that much, but essentially, your material must be at least 1/4 wavelength thick for it to noticeably affect a frequency's energy level. For example, at 250 Hz, your wavelength is 4.5 ft. 1/4 WL is 1.13 feet. This means that to make a meaningful change in the energy level at this frequency, you need ~1 ft of solid dampening material such as an elestic polymer. With rockwool or fiberglass panels (note this is not fiberglass like a boat deck, more like the pink insulation in your house but denser and in a solid panel) you can go with a thinner layer due to the slowing nature of the material. If you're using a denser material, such as lead, your thickness can be even thinner due to the way the lead tends to "oppose" the wave's energy, rather than converting it to heat. As a reference, WL at 100Hz is about 11 feet. 1KHz is about 1.1 feet. 3 KHz is about 4 1/2 inches. All this to say, the spray on stuff will work ok at higher frequencies, but won't do diddly for lower freq's. If you're looking to quiet your motor, this isn't the right stuff. If you're just looking to dampen vibration noises in other materials such as your sole, this would probably work pretty well. In sound control, there is no shortcut and there is no substitute for mass. Lead sheets like Tim used are by far the best way to dampen your engine compartment. As another reference, the density of Silent Running is just about 1/10th that of lead, you'd need 10x the amount of SR to compete with Lead.
Hopefully I wrote that in an understandable way, I'll look at it tomorrow when I wake up a little more and make any corrections if they're necessary.
Edited on 08/19: I forgot to mention this about material thickness. The quick and dirty way to explain why we use mass to control sound is this: If you have a wave and it encounters a surface, that wave will try to cause that surface to vibrate at the same frequency and energy level. This is a major component of why you hear your kid's muffled stereo outside their closed bedroom, their walls are re-radiating the wave into the space on the outside of the room. Now, to use an analogy, if you drop a pebble into a puddle, you see ripples flow out from it. If you drop that same pebble onto a concrete sidewalk, you don't see any ripples...why is this? The concrete sidewalk has much more mass than the puddle. So, if you have a sound source you want to control to prevent it from coupling into another space, you want to close off all the air passages you can and put a barrier with a lot of mass between the sound source and the other space. If your barrier has enough mass, the sound source will not have enough energy in it to cause the barrier to re-radiate the sound audibly into the other space. This is why we use lead sheets in engine compartments, because there is much more energy in low frequency sound, so it takes more mass to control it. This is why your kid's stereo is muffled. The walls of his or her bedroom have enough mass to control and not re-radiate the upper frequencies in an audible fashion, but not enough to control the lower frequencies.
Keep in mind, I've done my best to condense all this into an understandable forum-sized message, so some things are oversimplified.
Hope this helps,
Tony Orchard
Vernonia, OR
Last edited by Tony on Fri Aug 19, 2005 3:02 pm, edited 2 times in total.
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Figment
- Damned Because It's All Connected
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Oh, I'm right there with ya, Tony. I actually paid attention in Acoustics class too. I do half-expect this stuff to be snake oil.
But part of me thinks that they may be onto something. The thing about thickness of material relating to sound wavelength..... yes, you need thickness to absorb the full wave. But that's really only purely true if the wave is a pure wave. Few sound waves outside of a laboratory are pure clean waves. Sound, in general, consists of big waves that have thousands of tiny waves and oscillations. This silent running stuff, if it converts the energy of those tiny waves and oscillations, could actually take a good bite out of the total energy of the wave (yeah, I know, sound doesn't really behave in an additive fashion, but you get my drift).
Remember, we're talking about noise attenuation, not elimination.
The density thing is the part I have trouble with. Even after the water evaporates (i.e. the paint cures), how dense can this stuff possibly be? I dunno. Like I said.... it could very well be snake oil.
But part of me thinks that they may be onto something. The thing about thickness of material relating to sound wavelength..... yes, you need thickness to absorb the full wave. But that's really only purely true if the wave is a pure wave. Few sound waves outside of a laboratory are pure clean waves. Sound, in general, consists of big waves that have thousands of tiny waves and oscillations. This silent running stuff, if it converts the energy of those tiny waves and oscillations, could actually take a good bite out of the total energy of the wave (yeah, I know, sound doesn't really behave in an additive fashion, but you get my drift).
Remember, we're talking about noise attenuation, not elimination.
The density thing is the part I have trouble with. Even after the water evaporates (i.e. the paint cures), how dense can this stuff possibly be? I dunno. Like I said.... it could very well be snake oil.
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Tony
- Skilled Systems Installer
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- Boat Name: S/V Bonnie Blue
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Well, their website says (after conversion to numbers I can understand) you're looking at 11.26 lbs/gallon, or 84.27 lbs/cubic foot. That does seem disproportionately dense for something that, according to the FAQ should have a 1/16" finished thickness. I'm not really impressed with their "technical" information. There's not a single mention of an actual acoustic property, like the absorption coefficient or NRC.
Anyway...
As far as the sound, yes, you're right in that sound isn't a pure wave, however when you are talking about acoustic materials absorbing sound, they work a lot like a bandpass (or stop) filter. If you take a complex waveform, run it through a narrowband filter and measure what you're left with, you get your "pure" wave back. In much the same way, despite the appearance of a complex waveform, acoustic materials will only affect the specific bands of frequencies they can physically do anything with. That is where material thickness comes in. There's more to it, but as I said before, this is oversimplified.
Let me be clear, I'm not saying this stuff is total snake oil, though that was my initial impression. What I am saying is that yes, as they claim, this material will probably do an ok job at controlling sound caused by secondary vibrations from your engine (IE: your engine runs, your cabinet vibrates, you hear sounds from the cabinet vibrations) as long as those sounds are in the upper register (5K plus) but it will do little with the lower frequency sounds. That's just a laws of physics thing. IF the density is as they say, it could do more with the 2K-5K band of freq's, but below that it doesn't compute. I read the comments on their website from happy customers, I'd bet a lot of the sounds they were hearing were really secondary vibrations and not direct sound from the mechanics.
-Tony
Anyway...
As far as the sound, yes, you're right in that sound isn't a pure wave, however when you are talking about acoustic materials absorbing sound, they work a lot like a bandpass (or stop) filter. If you take a complex waveform, run it through a narrowband filter and measure what you're left with, you get your "pure" wave back. In much the same way, despite the appearance of a complex waveform, acoustic materials will only affect the specific bands of frequencies they can physically do anything with. That is where material thickness comes in. There's more to it, but as I said before, this is oversimplified.
Let me be clear, I'm not saying this stuff is total snake oil, though that was my initial impression. What I am saying is that yes, as they claim, this material will probably do an ok job at controlling sound caused by secondary vibrations from your engine (IE: your engine runs, your cabinet vibrates, you hear sounds from the cabinet vibrations) as long as those sounds are in the upper register (5K plus) but it will do little with the lower frequency sounds. That's just a laws of physics thing. IF the density is as they say, it could do more with the 2K-5K band of freq's, but below that it doesn't compute. I read the comments on their website from happy customers, I'd bet a lot of the sounds they were hearing were really secondary vibrations and not direct sound from the mechanics.
-Tony
Tony
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Figment
- Damned Because It's All Connected
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Yeah, I asked at Newport if they had any NRC or STC numbers, and I think the response was something to the effect of "This is a really new product for us and we haven't yet sold enough to pay for that kind of certification".
Reduction of secondary vibration will be a welcome achievement. Really, I think it would just be nice to be able to stand in the cockpit and communicate to someone standing in the cabin without shouting.
Reduction of secondary vibration will be a welcome achievement. Really, I think it would just be nice to be able to stand in the cockpit and communicate to someone standing in the cabin without shouting.
Last edited by Figment on Thu Sep 24, 2009 3:58 pm, edited 1 time in total.
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Figment
- Damned Because It's All Connected
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oh, I should probably report: One very heavy coat sprayed this morning.
I'd rented the sprayer for the day, thinking to spray a coat at 8:00, wait a few hours, spray a coat, wait until 4:30, spray a coat, and then race back to the rental shop with a helper cleaning out the sprayer in the back of the car.
No dice. The sprayer was constantly jamming and near-impossible to control. A thin coat just wasn't happening. I did a full spray, then looked over into the paint bucket to see that about seven pints of the gallon had already been used, so I just sprayed the last pint on the hard-to-reach spots until it was gone. Too bad the sprayer rental wasn't being charged by the hour.
I suppose that if I'd limited the effort to the surfaces immediately adjacent to the engine, the one gallon would have been enough. I was shooting for the boat's nether reigons, though. waaay back under the cockpit sole, waaay up behind the galley, etc. I think I'll need another gallon to finish the job, but only to build thickness on the easy-to-reach surfaces, so I won't bother with the sprayer again.
I'd rented the sprayer for the day, thinking to spray a coat at 8:00, wait a few hours, spray a coat, wait until 4:30, spray a coat, and then race back to the rental shop with a helper cleaning out the sprayer in the back of the car.
No dice. The sprayer was constantly jamming and near-impossible to control. A thin coat just wasn't happening. I did a full spray, then looked over into the paint bucket to see that about seven pints of the gallon had already been used, so I just sprayed the last pint on the hard-to-reach spots until it was gone. Too bad the sprayer rental wasn't being charged by the hour.
I suppose that if I'd limited the effort to the surfaces immediately adjacent to the engine, the one gallon would have been enough. I was shooting for the boat's nether reigons, though. waaay back under the cockpit sole, waaay up behind the galley, etc. I think I'll need another gallon to finish the job, but only to build thickness on the easy-to-reach surfaces, so I won't bother with the sprayer again.
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Figment
- Damned Because It's All Connected
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Yeah, sewing-machine.Tim wrote:Gee, I thought Atomic 4s were supposed to be all sewing-machine quiet and all...? ;<)
I think a lot of the sound transmission in my cabin is due to the absence of the icebox. The not-so-well-fitted 7/16" plywood in its place just ain't cutting it. On our block island trip last year, this cavity was stuffed full of baggage and groceries, and the cabin was remarkably quieter when motoring.