A question on sound deadening?

[Elkman]

Lots of companies selling sound dampening partitions for standby generators. If it is for a new installation and you have enough space, building a concrete pad with cinderblock walls and a roof to enclose the generator will be the most effective in terms of cost and noise reduction.

I have been at island resorts where generators run most of the day and every day and they are in a concrete room and so the noise is only apparent when the door to the generator room is open.

[Morich]

Sometimes chasing info on the net is a process of working through the correct terms to use in the search!

I did some looking around and finally came across the right bit of info for using water to quiet the genset here:
https://bb-rv.com/how-to-quiet-a-generator/

Maybe not as helpful as hoped as it is the last of eight ideas and fairly skimpy on details but it does have a couple points and indicates an idea of the reduction one might expect.

A small DB decrease of 5-10 doesn't sound worthwhile at first but if we factor in this info as being true, it might be much more than we first think.
Cut and copy quote:
Each 3dB increase doubles the sound reception and the annoyance or discomfort that goes with it.

So if a bucket of water can get you 5-10 DB improvement, is that worth it to you?
Since it seems pretty simple to use a bucket and water, you folks who do lots of camping/boondocking and use portable generators, may want to consider the idea.

[imnprsd]

How about digging a hole with vents for air intake and exhaust? ...but will it overheat?

[Morich]

Originally Posted by imnprsd

How about digging a hole with vents for air intake and exhaust? ...but will it overheat?

I had actually considered a hole and letting the earth be the absorber for noise but then I thought of some problems more specific to my area.

This is an area just East of what is locally called the "hill country" where the land shifted and lifted several hundred feet along the West side of what is now the I-35 highway. As a result of the geology, this part of the area is a vast limestone deposit with only a very thin layer of topsoil. This is not the type limestone I'm used to which is layers and lots of cracks, but one totally solid block that is miles and miles and very deep with very little cracking.

One reason for the lack of basements in this area is that they just become sunken septic tanks as rain water fills them and doesn't run out!

if I go down, first it would be a real pain to get deeper than 12 inches and then It would need to have a pump to get the water out any time it rains.

So I will do as the early builders and go for "ranch" style and build sideways, since I can't go down! Can you picture a ranch style generator shed? Shotgun style maybe?

[imnprsd]

I know about Hill Country since I once lived in Austin. It should have been called "Rock Country" or "Cedar Country," but that's a different story/problem.

What about making a 4-6" platform so you are above the rain run off... and then surrounding all sides with dirt up to the height you need? No doubt you have a LP gas line or large propane tank to supply all the fuel you need. So by making a "Sweat Lodge" ...with and intake and exhaust port, that will kill the noise... but what about the heat from an air cooled motor?

...Still sounds like more trouble than it's worth.

What about getting your neighbor to share the wealth? ...And costs?

Then you can pick up a bigger generator and share the power (and noise) when you both need it?

[Morich]

We have a small group of four who are interested but it seems I'm the only half qualified techie and they are hoping to see what I come up with and then decide if it is worth doing. Streets and such do not allow a combined effort other than side by side locations and we have discussed the factor of sales value when one moves and the cost is low enough to make combined efforts not practical.

We are generally an older, more experienced group who have had property sales issues so we don't want to set up any of those things to fight in the future. Appraisers and loan folks do not like anything "unusual" to think about and tend to just turn a deaf ear to anything that they don't understand. It's cheaper to buy our own genset than to try to untangle any easement/ownership questions later. But we are also only talking in the $1000 or less range.

The idea of dirt for sound control is something to think about but I'm leaning more toward a form of concrete for weather/ soft for decouple/ solid panel and soft inside as a cover. A concrete block cover would seem nice but the access is a pain in the gazebo! We can keep the overall size down to under 3-4 feet, so dealing with the exhaust is still the bigger point.

Cooling is for sure an item but not too hard to work out as I have lots of small air handler items handy. I have a big space out in back where things that have absolutely no use tend to collect and find their new use at some later date! And my wife calls it junk! When speaking of a 2X2X2 space being only 8 cu ft a bathroom vent fan pushing
60 cfm will pass a lot of air, even with losses from venting to avoid passing noise. Since there are outlets on the genset, wiring for venting is no problem.

My original purpose of posting was to find some experience with water baffling for the exhaust but that hasn't shown up , so I will just go with testing and change if needed. It may come down to being a simple retrofit of the exhaust to a flex pipe and run it into a bucket set in the ground and filled when needed!
That does still bring some questions like how to run a hot exhaust into a plastic bucket, so some type of collar may be needed.

One of the advantages of only working when I feel like it is that time spent on DIY projects is no longer a big deal to figure in on the planning! I'm near $650 depending on the price of the "junk" used, so I'm feeling okay, so far.

[Elkman]

Sound will travel over a wall, ask the people living in houses behind the tall walls along the freeways. Only by completely enclosing the generator on all sides and the top can the noise be significantly reduced for you and for your neighbors.

I don't live in Texas (been there and escaped) but even with the dismal power grid I would consider how many days without power at your house and how much the generator will need to run each year. My standby generator runs on natural gas and in California the supply is steady 12 months of the year so it has worked out well. This would be a problem in Texas where I would be looking into a diesel generator and installing a very large diesel fuel tank near it.

There comes a point with many projects where it is best to stand back and reconsider ones options and validate the assumptions that have been made.

[SmilingSimon]

seems you need to go Solar panels, you are pretty picky on the quiet aspect so non motor may be the answer, even a wind powered gen ?

GL

[Morich]

It's been a while since I first brought this question and the progress has been slow for a number of reasons. First was actually getting hands on a generator that I wanted as they have been caught up in the supply train shortage and none were on hand for a while and then there was just a lack of motivation to get on it as the supplies I first wanted were not in stock.
As a result it has taken way too long for a small project but on the good side, I was given plenty of time to look over and sort through tons of options for materials to use and came up with lots of alternates which seem to work fine and I was able to get for very little other than using up lots of the "handy" stuff stacked around in the garage.
My wife thinks that may be one of the best things about the project as I did clean up/ use up a number of things that have been hanging around too long!

But I'm now down to calling it nearly done and wanted to let you folks know what I have done to get a generator that is big enough to do all the household items I consider necessary and some which I call just nice. As mentioned, being quiet was also a big priority as well as keeping it portable so that it is not out in the weather full time but can be rolled out and put together as needed.

For the portable part, I went with a Champion 4000 surge/3500 run watt dual fuel inverter hybrid generator so that I can store several 20 pound bottles of propane without worry about it going bad, then added the wheel set for portable and a DIY cover to control the noise as the larger size generator is somewhat more noise than some of the smaller that would not have done some of the items I wanted to run.

For materials, I had most of it on hand but wasted some effort and money trying to glue up sheets of a plastic foam type material but gave up on it and used simple layered sandwiches of cardboard, compressed fabric shipping padding in a lightweight wooden frame and pink foamboard as the outside layer.
The study I did says there are tons of ways to go with materials but one thing to keep in mind is that each type has advantages as well as disadvantage and we need to also keep in mind that each type does different things for the sound we want to control.

My first step was to make slanted walls to deflect the sound toward the ground, where I DID NOT want a solid surface like concrete which would reflect the noise but I used the ground as a second soft area to absorb the sound waves. A 2X4 frame laid on the ground with cardboard to deflect down into the ground.

Then the second space was filled with 2" thick compressed fabric that was used shipping materials which I picked off Craigslist. It is easy to work, reasonably lightweight , cheap/free and does a good job of absorbing the sound. Not hard to work, once I got around to trying the radial arm saw to cut it! A dust mask was needed but it was quick and easy!

Then as a semi- weather resistant outside, I used scrap 3/4 inch foam as another layer to both deflect a bit but also absorb the vibrations that reach it.

I have found that the exhaust is not really a big problem after getting to this point as I simply let it out inside the cover and use more venting air to carry the heat out. I had thought to add a muffler on a 1/2 inch pipe but find it not needed. The venting is critical for this to work but turned out to be quite simple as I had things on hand. A meat thermometer shows the exhaust air as just short of 120 degrees, which isn't bad when we have 94 ambient today!

For venting, I knew I wanted plenty of air and one of the things that worked really well for that was a surplus fan from an old microwave! They move a lot of air and the 110ACV worked out handy due to having plugs on the generator face for easy access. I had to design a box of plywood on the side for pushing air in so that it did not leave the motor in the hot air coming out, then also a vent on top set up to allow for air to come out but not in a direct line so that sound waves would follow. Air easily flows around corners but sound doesn't!

So the result is one 2X4 frame laid on the ground, four side sections leaning in and one top laid on it all. Somewhat weird looking pink that will eventually get painted but it all lays down flat in storage and the generator rolls inside very nice. One of the hangups on the progress was getting the interlock switch for the outside breaker panel as they seemed to be extinct for some time!

It fits what I wanted at just under $600 with sound readings that I love!
Nearest property line, which is also one of the neighbors most likely to tie on if we need it is 52 DB, at the sidewalk in front 40 DB and in the house, nearest bedroom, around 10-15db but hard to measure as my breathing is picked up too well at that low level!
Less noise than the average lawnmower!

I'm happy and I'm done!!!

[imnprsd]

Thanks for sharing your conclusions and tips about reflecting the noise at an angle and leaving a ground perimeter around the generator to absorb noise; plus your intake and exhaust porting looks good... and no engine modification required. I also like the top lid being larger.

Is the generator just sitting on it's frame with wheels in the dirt?

And with the enclosure you built your noise level dropped by ~14-17dB? What did you start with on this model of generator?

Note: 52DB is the loudness of a portable AC in the home so it sounds like you very much achieved your goals.

Question: I wonder if a steaked-tarp draped over the top would lower the noise even more... and weather protect the enclosure and LP tank. But I bet you already thought of this.

Otherwise, are you going to paint that bare wood or put shingles on it? I would think you need some more weather protection?

[Morich]

Lots of the decisions were based on getting exactly what I felt was important to me in this one case. First was the thought that I wanted it as quiet as possible and certainly in the area where we can run it all night if wanted without too much bother to any neighbors.
Sound ratings are a weird mix of things without too much real spec on what and how those sound levels are measured, some are more inclined to sales than truth?
But at 7 meter/about 23 feet seems to be one general level to test and this one rated at about 62-64 DB and does match what my low level cellphone app shows.

So I got the noise down to well within what I want as we can sleep well with it running.

Second big step was keeping it portable or at least easy to move in and out as we don't expect to use it often, just want it when we want it and without a lot of cords for hazards or trouble to place it. I added an interlock and 30 amp outlet to the breaker box outside. This house was wired by an electrician as it was built for him and he did lots of work which made the change pretty simple. He kind of got carried away at times and it is interesting to figure at times but all interior circuits are 20 amp, rather than the mix of 20 and more 15 amp that we usually expect.

That left using a 30 amp generator to power a normal 200 amp house to be a matter of choosing which were my "priority" and putting them over to the single 110 leg powered by the generator. Since there is a breaker panel outside which then feeds a sub panel inside and the inside has all 20 amp breakers, I did not have to even move the breakers themselves but pull the wire out of one and swing it to the other as they are all 20 amp!
We spent far more time debating and testing each item in the house to see that we were certain what load was moved to avoid getting the load too far off balanced.

Notice how the AC is setting slightly askew on the concrete pad? That is to allow JUST enough room to get the RV in past that point, so adding a genset to set permanently was not going to be easy as we are cramped! The options got into moving the genset to the other side of the AC which then semi-blocked the gate, making the enclosure tighter which made noise control tight as we don't want it touching the inside to transfer vibrations directly outside, OR go with killing two items at once.

One I don't want it out in the weather full time and also I don't want it in the way, so portable, stored inside hitting both those biggies! I have room, just not room where I wanted it? So if it isn't normally out except for me to run once in a while, which is less needed with propane as it doesn't sludge up like gasoline, it doesn't need to be as weather tight. Mounting is not the correct word as I plan to just dig a small notch for the wheels to drop into when setting it out. If it rains, water will be running under it all but I'm okay with that.

Weather resistant but it does need to be easy to take apart and storing flat was a major thing to store better. The sections come apart easy and lay flat against the wall, only taking about 4' by 4' and about 10 inches out from the wall where I strap them. Kind of like getting the kids block set back into the box it came in? Turn it all the right way and it fits like a glove!

I do plan to paint it at some point but that is more likely to happen when I'm painting something else and not really needed too much if I never use it in the rain! This has been a strange year around here and we have been having rain but I consider that not likely to last long. I have a variety of different things that might get involved as I see what weather might be doing at the time. I might throw a sheet of plastic over part of it and leave one end open for cooling if for rain, but I also have some old moving blankets that could be used at times also. Just kind of leaving it open until I see what motivates me at the time!!!
Lack of motivation seems to be a major problem!!!

[imnprsd]

Thanks for sharing. I learned a lot.

I have been tracking posts like this to see what can be done to lower the db levels of my Onan 7500, but nothing seems to work without some consequence to the motor.

Building a portable deflector might be the answer. I.e., if someone borrows your deflector idea, and makes a portable ramp, or they use a small 45-degree tarp off the side of the RV... to deflect the Onan exhaust and noise, I wonder if that will help when camping nest to other people?

[Morich]

I feel a tarp might not do what is needed as it works best by using several different methods.
One is to deflect using a firmer, harder surface as the stiff material tends to deflect the wave back, rather than let it vibrate that material and pass the vibrations on to the other side. The reduction from the deflection, means the next layer has far less to deal with and that is where a softer item is okay as a way to let the vibrations move into the material and if we use something like fiberglass or the compressed fabric, like I found the individual strands tend to give at first but separate and divide the waves of sound into smaller waves that tend to bounce around in the many, many strands and kind of "get lost", before what little remains works to get the last hard layer to vibrate enough to move the air outside.

That's the really low level tech as I understand it and I'm certain a number of higher level ideas are involved but it makes my head hurt to think much higher than three levels of theory I can't see! Looking at boat waves and how to break them and reduce the damage, it seems to relate.

In shore damage control, you want to first deflect it to some other place, break it into smaller waves and then you can deal with what is left! Seems sound waves work the same, so I went with whatever cheap items I had and found most was on hand if I could figure how to fit it together and still leave it easy to take apart and store.

For a genset built into an RV, it gets tough, just due to the fact we have less choice on where to fit the genset and would have to work the noise abatement up on the side or rear as well as down lower between the RV and ground. There was a really cheap ($10?) board when I was looking and I considered it but I now see it is $3 dollars higher in the last month!
https://www.homedepot.com/p/1-2-in-x...8096/206086210

It might be something worth looking at for leaning at an angle to deflect as well as the fibers are somewhat soft and will move to break the waves as well as each tiny fiber has to vibrate and pass it along to the next before it gets to the outside.

On an RV where storage is precious, setup is hard, I'm not sure it works well enough to fight the fight! Just that things start so high off the ground makes the sides be too large to store?
Perhaps something semi-heavy/ bulky like moving blankets could be hung on some form of hooks? Pain to have to crawl under to hang it there but if we want to get as much reduction as possible, it needs to be pretty much ALL the possible outlets.

With enough layers, it could be done but whether it is worth it, is a big question!