Something Random

time

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Even so, I can't see even Cougtek crushing Stereodude's construction. Four inches of timber reinforced with cripple studs connected to a further four inches in the top plate.

Perhaps Coug relies on trained termites?
 

Stereodude

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Out of curiosity, why did you choose to not attach the room to the floor above.
It's for sound isolation purposes. It is attached, but not directly. It uses PAC RSIC-DC04 clips to attach the walls top plate to the joists overhead. That way vibrations (ie: sound) are not passed into the floor overhead.
 

Stereodude

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Cool that thought occurred to me but I didn't want to say anything, wasn't sure.
The room has / will have all sorts of design considerations for sound isolation purposes. That why I have the stagger stud wall, why the perimeter walls are not attached to the concrete walls, and the two 2x4 walls with the 1" gap between them that the doors go in.

There will be two flush 36"x80" solid core 1 3/4" thick interior doors in exterior frames to create an airlock at the entry. I picked up the doors today. It took a week for Home Depot to get them in after a special order.



The ceiling won't be connected directly to the bottom of the floor joists either. I'm going to use Kinetics IsoMax Clips to decouple the ceiling from the joist. Then I will be using two layers of 5/8" thick drywall with Green Glue in between them for the walls and ceilings.
 

ddrueding

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All the steps you are mentioning are ones I'm considering for the master bedroom. I am a very light sleeper, and it would be great to have a place that is actually silent.

Helps keep noise in, as well ;)
 

e_dawg

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SD, since you seem to know quite a bit about building construction and acoustics, wondering if you had any ideas about my noisy A/C problem. I posted this on HT Shack.com, but wouldn't mind your take on things:

I have been scouring the net trying to find an optimal solution to quelling the noise from my noisy outdoor A/C condenser unit, and my search has led me (surprisingly, at least initially) away from HVAC forums and towards acoustics, studio, and HT construction forums.

I have a relatively new (first summer of use, came with the house) 3.5 Ton entry-level KeepRite split central A/C system, and the condenser unit is situated along the side of my house that is adjacent to my neighbour. The compressor noise and vibration is noisy enough that it disturbs both my neighbour and i. Unfortunately, the condenser unit is on the side of my house where the study/library, family room, and HT/music room are. Even worse for my neighbour, her bedroom faces the condenser unit.

The mid-high frequency buzzing of the compressor and the hash of the fan is not too bothersome as long as the windows are shut tight against their seals, but the low frequency hum and vibration goes right through the ground / wall / foundation such that i can hear and feel it on both the main floor (family rm) and basement (HT/music rm), and my neighbour can hear and feel it in her main floor bedroom. Believe it or not, the condenser unit is sitting on foam-rubber blocks already, yet the vibration seems to go right through them.

I contacted 2 HVAC people in my area, one of whom came to physically inspect the A/C unit, and the consensus conclusions are as follows:

1. I have a cheap condenser unit, which is noisier than premium units as it does not have a dual-stage compressor, the compressor is not mounted to the base of the unit using rubber mounts, and it doesn't have a sound blanket.

2. It is technically possible to move the unit around to the backyard and put it under the deck, but both contractors recommended against it, saying that (a) it would be quite "invasive" and expensive re-routing the lines in the house; (b) there would be too much pressure loss along the line, resulting in low efficiency / cooling power, and (c) placement under the deck would result in restricted airflow, lower efficiency, and potentially just as much noise due to resonance under the deck.

3. The two best solutions from the HVAC contractor's perspective are: (option 1) wrap the compressor unit inside the condenser with a sound blanket and use softer rubber pads under the condenser unit (the foam-rubber blocks seem to be a bit too hard) (cost: $300-400), or (option 2) replace the condenser unit with a premium dual-stage model (cost: $3-4k).

Our neighbour is willing to help us defray some of the cost, depending on how effective the solution is. Naturally, she would only be able to help out so much if we were to spend a fortune on a new premium condenser unit. And my preference obviously is to avoid spending too much money. This has led me to the path I am down now: going with option 1 from an HVAC based solution and supplementing it with sound treatment solutions. It is my hope that the combined solution can give me superior results to getting a new condenser unit at a cost that's much closer to option 1.

Because the condenser is in the "alley" between our two houses, there seems to be a standing wave / resonance effect that is amplifying everything. Furthermore, because the majority of the noise seems to be vibrational from the compressor, i think the focus should be on stopping the noise and vibration at the source: the condenser unit and the virtual "room" created by the walls of our two houses. Ultimately, this means:

1. decoupling the condenser unit from the ground
2. damping resonance of the sheetmetal cabinet of the condenser unit, and
3. absorbing the standing waves between the two walls

So my questions are: 1. Do you think i have evaluated the issues and possible solutions properly, and 2. How might i best go about implementing the above three tasks?

I have posted a series of pics that illustrate the situation i have described above in the following gallery. Would appreciate if you could take a look and let me know what you think:

http://www.smugmug.com/gallery/13109...50588671_JBAxj
 

MaxBurn

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A couple thoughts.

I know there are rubber feet out there that are designed to keep transformer hum from transferring to the building, look for some of those. They work surprisingly well and we put them under UPS systems that generate a lot of noise.

Slap some dynomat on the compressor and inside the sheet metal. Also get some self tapping sheet metal screws and make the sheet metal more secure. Maybe you could take all the sheet metal off and make yourself a more aesthetic and quiet wood enclosure.

Mind obstructing any air flow, not only does it cut down efficiency but it can kill your compressor due to high head pressure situations.
 

Stereodude

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Unfortunately, your link doesn't work...

So basically, you have one of these outside and it's too noisy? What is it sitting on? Is it sitting on a concrete slab? If so, what else is the slab touching other than dirt?

Basically you need to figure out the source of the noise. Is the compressor causing the whole thing to vibrate which triggers some resonance? If that's the case you can perhaps isolate the compressor from the enclosure to reduce the vibrational energy transferred to the enclosure and perhaps add some mass (using something like Dynamat) to dampen the enclosure by lowering the frequency at which is resonates which will make it quieter (by preventing it from entering resonance). Ironically the foam rubber blocks it's sitting on could make the noise worse by allowing the metal to vibrate more easily.

With regards to vibration, it seems hard to believe that it vibrates enough to transfer vibrations into the house through the concrete slab and into the dirt and back into your house and your neighbor's house. I have a crappy 3 year old builders grade Bryant AC unit outside and it's pretty quiet. You basically can't hear the compressor only the air moving from the fan. It's just sitting on a plastic capped slab of concrete about 1 foot away from the house.
 

e_dawg

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So basically, you have one of these outside and it's too noisy? What is it sitting on? Is it sitting on a concrete slab? If so, what else is the slab touching other than dirt?

Yep. That's the one. It's sitting on 4 foam-rubber blocks on a concrete slab on the dirt.

Basically you need to figure out the source of the noise. Is the compressor causing the whole thing to vibrate which triggers some resonance?

I think that's a large part of it, especially during start-up. There is a massive droning noise when it cycles on and it tapers off to a throbbing hum.

With regards to vibration, it seems hard to believe that it vibrates enough to transfer vibrations into the house through the concrete slab and into the dirt and back into your house and your neighbor's house. I have a crappy 3 year old builders grade Bryant AC unit outside and it's pretty quiet. You basically can't hear the compressor only the air moving from the fan. It's just sitting on a plastic capped slab of concrete about 1 foot away from the house.

Do you think the unit is defective? I think it also has to do with it being in an alleyway, which is acting as an echo chamber.
 

Bozo

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Maybe these would help. Both under the compresser and the outdoor unit.

I wouldn't wrap the compresser; I'd be affraid it would overheat. Maybe make a cage of sound absorbing material that leaves an air space around the compresser.
 

Stereodude

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After looking at the pictures I have a few more thoughts. I wouldn't waste any time on Mass Loaded Vinyl. It's basically worthless. Soundproofing is achieved my making things airtight, adding mass, and preventing resonance. MLV is not very good at any of those three.

My first suggestion would be to put the concrete slab on a dirt / sand mix instead of that crushed stone. I would remove all the stones from under it and build up the area with something like a pea gravel / sand / dirt mix. Then put the slab on that. Next I would try to replace those rubber blocks (assuming they're rubber) with something that drastically increases the surface area contacting the bottom of the enclosure and the slab. For a quick test I'd try a piece of OSB or something. The bottom could easily be vibrating like crazy because it's not well supported. In my unit the compressor is in the center and you've got no support under the center so you could be turning the whole enclosure into a sounding board (like a guitar or other stringed instrument). Then you can always use dynamat or an equivalent product (I like Peel and Seal) to add significant mass to the large flat areas of enclosure to further reduce resonance.
 

Stereodude

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I think that's a large part of it, especially during start-up. There is a massive droning noise when it cycles on and it tapers off to a throbbing hum.
That definitely sounds like a resonance issue. I'd try out some of the suggestions I've already made to reduce the resonance of the enclosure. A quick test would be to push on various flat panels while it's running and see if you can change the characteristic of the noisy by effecting the resonance of the panel you're pressing on.
Do you think the unit is defective?
I suppose that's possible, but it's hard to say unless you find someone else with the same unit under very similar circumstances and compare.
I think it also has to do with it being in an alleyway, which is acting as an echo chamber.
I'm sure that's part of it as well. You should be able to get the resonance under control, but if it's still too loud you may need to look at building some sort of fence / enclosure around it and have several inches of compressed fiberglass (outdoor rated of course) to try to absorb the sound leaving the unit horizontally and direct the noise more upward. Obviously you would need to leave enough space for the unit to get ample airflow.
 

e_dawg

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Next I would try to replace those rubber blocks (assuming they're rubber) with something that drastically increases the surface area contacting the bottom of the enclosure and the slab. For a quick test I'd try a piece of OSB or something. The bottom could easily be vibrating like crazy because it's not well supported. In my unit the compressor is in the center and you've got no support under the center so you could be turning the whole enclosure into a sounding board (like a guitar or other stringed instrument).

Unfortunately, the bottom of the unit is far from flat. It is raised and domed in various sections.

Also, I was under the impression that one should try to minimize contact between the unit and the slab to try to decouple it as much as possible, as opposed to trying to increase the amount of surface area touching the slab?
 

Stereodude

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Unfortunately, the bottom of the unit is far from flat. It is raised and domed in various sections.

Also, I was under the impression that one should try to minimize contact between the unit and the slab to try to decouple it as much as possible, as opposed to trying to increase the amount of surface area touching the slab?
That all depends what you're trying to do. If you want to minimize transferred vibrations, maybe. If you want to minimize resonance of the bottom of the unit, no.
 

MaxBurn

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Can you explain this to me so i get a better idea of how it works?

You want to troll some HVAC forums for a proper explanation but all I am saying is don't block any air flow of your condenser coil IF you are thinking of putting some sort of covering over the thing to block noise. You would have to go to some really great lengths to do it right so IMO just focus on killing the noise conduction to the ground and stopping it at the source.

I'm having some second thoughts on wrapping or covering the compressor myself and I just don't know.

Ask here, great forum:
http://hvac-talk.com/vbb/index.php
I go here from time to time for the controls section.
 

MaxBurn

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What is up with people, I just had two people back out of deals that I was going to buy stuff from. It was at the point where I had paid and was just waiting on shipment notices and they just refund my paypal. You think people out there are funding bills for the end of the month on fake stuff just so they can float over to the next paycheck?
 

MaxBurn

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Used computer parts, only one out of three deals last week went right. Thought I would give ebay a break, I'm guessing that was a mistake. Whole heat score thing doesn't seem to mean much.
 

time

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E_dawg, why on earth did you bury this in the random thread?

Do you think the unit is defective?

How old is it? Has anyone checked the gas pressure?

A quick search of the net found at least one other guy who claims his unit is whisper quiet. And it's a scroll compressor, which should be quieter than the older reciprocating piston types. So yes, there's a chance it's defective.

I'm pretty skeptical about wrapping the compressor itself, despite KeepRite portraying it as a bonus feature. It might reduce some buzzing - although that will transfer through the attached pipework anyway - but the fiberglass layer won't do much at all, let alone magically stop low frequency vibration. Also, compressors are not 100% efficient, so they have to get rid of at least some heat.

There's a slim chance that either shipping spacers weren't removed or rubber grommets not fitted to the compressor bolts during installation. That would make the whole case vibrate pretty spectacularly.

You may be getting vibration conduction through the pipes to your house, which BTW is damn close to the unit - possibly close enough for some low frequency induction? Put your hand on the wall in different places and check, and try holding the pipes.

To me, your "slab" looks ridiculously puny for a near 200lb(?) unit. I would have expected a solid base, not something that probably only weighs 50lb. Combined with the fact that it in turn is sitting on an unstable base, i.e. where it contacts the tips of the gravel, it seems inevitable that the unit is going to vibrate. Thick isolation blocks like you have only encourage it to dance around even more. And I notice that they're not even attached to the unit, let alone the slab!

Ideally, it would be bolted to a massive base with just some waffle pads or isolation material as required. Less is more, check out some industrial machinery mountings.

I'm also wondering how much noise is coming through the top with the fan. Again, given how close it is to the wall, you have to wonder about the acoustic effects, eg. if you put an audio speaker next to a wall (and especially the corner), it dramatically increases the bass.
 

Bozo

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When you are done with the outdoor unit, you might consider some plants along the neighbor's house and along your house. Leave plenty of air space around the unit though. Check with a local gardening store on some plants that won't grow over the roof or make your passage way unpassible.

You'd surprised at how much noise plants can absorb. And they will help tons with the echo affect.
 

jtr1962

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Don't overlook the possibility that the metal enclosure could be acting as a speaker. I actually had that problem while trying to quiet down a PC. Everything was isolated, but the sound waves propagating through the air caused the case to vibrate. A thin sheet of polyurethane foam glued to the inside of the case solved that problem.
 

e_dawg

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E_dawg, why on earth did you bury this in the random thread?

Because i was reading SD's discussion about his basement construction and sound isolation suggestions to MaxBurn and thought it would be a good idea to continue the conversation, so to speak...

How old is it? Has anyone checked the gas pressure?

It came new with the house. This is the first summer we are living here, so it's been used all of 3 months. No, the gas pressure hasn't been checked. We didn't think to check, as it's basically a new system. Is the noise a sign of too high/low pressure in the lines?

A quick search of the net found at least one other guy who claims his unit is whisper quiet. And it's a scroll compressor, which should be quieter than the older reciprocating piston types. So yes, there's a chance it's defective.

Do you think a crankcase heater would help?

It might reduce some buzzing - although that will transfer through the attached pipework anyway

So how does one deal with that? I assume all A/C units are the same in this regard? Much of the pipe is already covered with a foam insulation jacket.

To me, your "slab" looks ridiculously puny for a near 200lb(?) unit. I would have expected a solid base, not something that probably only weighs 50lb. Combined with the fact that it in turn is sitting on an unstable base, i.e. where it contacts the tips of the gravel, it seems inevitable that the unit is going to vibrate. Thick isolation blocks like you have only encourage it to dance around even more. And I notice that they're not even attached to the unit, let alone the slab!

Ideally, it would be bolted to a massive base with just some waffle pads or isolation material as required. Less is more, check out some industrial machinery mountings.

I was under the impression that most residential A/C condenser units just sit on a concrete or plastic slab...
 

LunarMist

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I was under the impression that most residential A/C condenser units just sit on a concrete or plastic slab...

Usually. However, that setup does look rather weak to me. Older homes designed for A/C tended to have a poured slab. Now I've noticed more that sit on a composite slab. They are also used for upgrades on old homes since newer AC/ units are larger. I suspect the compresser is a noisier than average one. Perhaps I missed it above, but do other homes in the neighborhood have the same compressor that you can listen to for comparison?
 

Stereodude

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Putting in a soffit of some kind?
Sorta... The ceiling with be a flat 8' except for the center area inside that framing which will be something like 8' 8". The plan is that the center area will be painted a dark red / burgundy color while the rest of the ceiling with be flat black. Then there will be some molding / trim around the perimeter of the center area that conceals rope light which will cause the center area to glow when lit. That frame took several full days to get up since it's not rigidly attached to the ceiling. It's hung from DC04 clips. Then there are a pile of upside down T shaped spacers hanging down from the joist that the IsoMax clips will attach to that took a long time to install. Then the hat channel will go in those yielding a decoupled ceiling at 8'. I still need to install a bunch of ~1" spacers in the center area (inside the frame) for the IsoMax clips to attach to there since the drywall needs to clear the gas line (and also be decoupled).

PS: A Tokina 11-16mm F2.8 is a handy lens to have when trying to take pictures of a room under construction.
 

jtr1962

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The ceiling is taking me forever and I'm still not done. :crap:
Join the club. I've found every time I've done anything at home it takes twice as long as I anticipated. Usually it's because something ends up being short or long by an inch or less.

Three years ago I put a new ceiling in the finished basement and also added a bunch of outlets plus several light fixtures ( a pair of 3 x 32W T8 lights and an incandescent fixture I modded with LEDs over the bar ). It took something like 2 weeks. Here's the album with some pictures I took of the ongoing progress:

http://s91.photobucket.com/albums/k318/jtr1962/BASEMENT RENOVATION/?start=all

Among the "fun" things I had happen was using staples which were too short ( because Home Depot didn't have the longer ones I wanted ). I glued the ceiling tiles on with Liquid Nails and also stapled them at the edges where they butted together. The idea was the staples would hold until the glue dried. Well, I had almost finished one section, got my mom to show her, and just as she came down the whole thing started sagging. I managed to wedge som furniture and boxes in to keep it from being a complete disaster, but I ended up redoing most of the tiles the next day when I finally found the longer staples.

Another "fun" time was when I ceramic-tiled the laundry room. Just when I finished grouting the area flooded because the neighbors had their kids out in a leaky kiddy pool. To this day the grout still looks gray. Maybe when I feel ambitious I'll just redo the whole floor.
 

Bozo

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I tiled our foyer floor and everything looked fine untile the grout dried. It was the wrong colour. The jerks at Home Depot gave us the wrong stuff. :arge:
 

Chewy509

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I tiled our foyer floor and everything looked fine untile the grout dried. It was the wrong colour. The jerks at Home Depot gave us the wrong stuff. :arge:

How much of a wrong colour? If the grouts too light, then a grout stain should work nicely.

I've used one in the past to turn grout that was going white back to a dark grey/black colour to match the tiles - the tiler must have had a bad batch of colourant for the grout or just mixed it wrong when he laid the tiles.
 

Bozo

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I ended up coating the grout with a stain to get it right. But what a pain. Now every few years I have to touch it up.
 
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