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Domestic noise suppression

srrxr71

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Since most of us live in situations that are suboptimal for music listening every optimization matters.


I had my HVAC replaced recently and these new R410 units are noisy. In fact even GLM warns me that the microphone is picking up a lot of noise and asks me before it calibrates.

Did some research and found a Brinmar compressor blanket. (Search exactly that on Amazon) about $80. This on its own didn’t make as much difference as I expected.

Also I found EVA sound isolation footers for the outside condenser unit (many brands on Amazon) about $24 for the 6” ones.

I installed them this morning and I can say the noise and vibration coming into the living room is much lower. Not as low I wish it were.

If I had space I would relocate the condenser unit but that is not an option for me. Any more optimization would involve located a professional knowledgeable about this - which I assume would be a challenge.

Even if I precool the house for listening sessions the fridge is still audible.

I’m wondering if anyone has tried acoustic absorption devices behind a fridge or perhaps on the wall between the condenser and my living room.

The noisy spectrum has definitely gone up in frequency. Before it was very bassy noise. Now it’s moved up into the midrange. That noise was probably already there just masked by the low frequency noise that was present before.

I wonder if anything would be effective to cut down the remaining noise.
 
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Tom C

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Hope someone has some answers. My furnace fan is louder than the AC, but the fridge!
 
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srrxr71

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Ok so I did some spectral analysis. Very clearly at 50dB in my listening position at 63Hz and 125Hz. I bet it’s 60Hz noise from the compressor and the 120Hz overtone.

First is HVAC off and second is HVAC on.

At least now I know which frequencies I need to target.
 

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DoubleWoofers

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Really? My new AC is much quieter than anyone I have had in the past. What exactly is the noise source? The compressor outside? Fluid moving in the pipes? Fan?

My fan is far far noisier than the compressor. I can sit by a door near the compressor and except when it turns on, it is hard to tell it is on. Now I should put the caveat that my AC is mounted on a concrete pad on the ground. Roof mount, and even side wall mount are much louder from being in other peoples houses.

Only way to reduce fan noise is to slow it down really. There are baffles you can get that reduce the noise. They are targeted at sound proofed / noise reduced room.
 

DVDdoug

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fridge is still audible.
Some people unplug the refrigerator (and turn off the HVAC) during recording but I've never heard of unplugging it for listening...

Psychologically, I'm not really bothered by these slight-normal noises. When it's coming from the speakers it's more annoying.

And of course, certain sounds or loud sounds or bass from the neighbor's stereo is annoying. If you're actually hearing 60 or 120Hz nose, that's probably more annoying than broadband noise like pink or white noise.

Soundproofing is a "big topic" and it's expensive!
 
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srrxr71

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Really? My new AC is much quieter than anyone I have had in the past. What exactly is the noise source? The compressor outside? Fluid moving in the pipes? Fan?

My fan is far far noisier than the compressor. I can sit by a door near the compressor and except when it turns on, it is hard to tell it is on. Now I should put the caveat that my AC is mounted on a concrete pad on the ground. Roof mount, and even side wall mount are much louder from being in other peoples houses.

Only way to reduce fan noise is to slow it down really. There are baffles you can get that reduce the noise. They are targeted at sound proofed / noise reduced room.
The fan is not the issue. It’s pretty quiet as it sits in the attic above the second floor so I don’t have any fan noise or even airflow noise.

There is airflow noise on the second floor by the intake but it’s about as quiet as one could expect it to be.

The main problem for me is that the condenser is literally across the wall from my listening space. From my speakers. Yes from my reading a concrete pad is a must for these and actually if you think about it increases the noise. It would probably be quieter sitting dirt or mud (but terrible for the stability of the unit).

The issue is proximity. As well as a fence on the other side. The space between it and the fence is barely enough for me to pass. This is a fairly urban area and plots are small and buildings are built taller for space. Some neighbors have 3 and even 4 story homes here.

So I put rubber/EVA isolators between the unit and the concrete pad. That helped a lot. Before it sounded like a rumble coming through my floor even. Now it’s more air transmitted 60Hz sound. The compressor inside got an Eva pad under it as well as a Brinmar blanket (keep in mind some units come with that stock - mine didn’t).

I walked around and I doubt the wooden fence is really sending that acoustic energy back. When I walk inside it’s clear the loudest sound is through the wall in the spot closest to the condenser. The walls are reasonably thick but we know dry wall isn’t exactly great at sound isolation and probably not so great at 60Hz.

The good (maybe bad?) it’s that the TV blocks the path of sound from the condenser to my MLP. But it seems to be reflecting it back which is why if I turn my head I can really hear the overtones.

Yes I hear side mount is notorious for noise but roof mount in my case would be above the bedroom or possibly the spare bedroom and not so much near the listening space. For sleeping one could get used to the sound. In fact so much so that I remember my grandpa’s house was built over a literal weaving factory and the entire house had sound and vibration. He would immediately wake up if the looms stopped. Whenever I visited it was cool because it sounded like the whole house was flying. It was a very comforting sound I have to admit. It was a very pleasant white noise as the entire building was built of concrete.


Why good? I could possibly place GIK sound blocks or an acoustic panel which could be hidden behind the TV but I would rather find an outdoor safe solution and place isolation outside. The bad? The TV mounting solution will not allow me to place acoustic panels in the area where it mounts.


It’s debatable whether this level of care needs is not be taken for listening but the entire point of moving here was to not have neighbors and to listen in peace to my audio system. Which means also that I can play at 90dB at which point of course I will forget the HVAC noise.

I could move everything to the opposite wall and then the sofa back would block the noise. That is a last resort but I would entertain it. I would at learn move the audio system over and then call over the TV installer to move the TV. The cost of moving the TV is quite significant but could be less than any further acoustic treatment. However I guess acoustic panels can always be useful and are an “investment” to a former audio-asylum inmate. Remember that forum? They are still around apparently arguing about cable risers and such.

For night listening I could always precool the place. It’s mostly for after work listening that this is an issue.

The latest good news is that I have moved the EVA blocks around and there seems to be an improvement. I have 4” GIK panels coming on Friday to deal with a 250Hz issue in my GLM trace. They might help too. If I can get it down about 10dB I would be pretty happy.
 
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srrxr71

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Some people unplug the refrigerator (and turn off the HVAC) during recording but I've never heard of unplugging it for listening...

Psychologically, I'm not really bothered by these slight-normal noises. When it's coming from the speakers it's more annoying.

And of course, certain sounds or loud sounds or bass from the neighbor's stereo is annoying. If you're actually hearing 60 or 120Hz nose, that's probably more annoying than broadband noise like pink or white noise.

Soundproofing is a "big topic" and it's expensive!
Absolutely, that 60Hz cranking noise is not fun. If it were white noise it would be tolerable. That’s why while I have lived in apartments where the fan noise was the main noise that didn’t really bother me much. This noise is different.


I think I’ll try outdoor solutions and see. Maybe even reflective to send it all to the thin wooden fence side.
 

DoubleWoofers

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It sounds like you have a noisy AC. The concrete does sit on dirt so you still have that mechanical isolation.

I am going to guess you have a single stage AC? I don't think they are any noisier than they were in the past.

The new variable speed units are super quiet. Most of the time they are running far below max. At max they are just as loud as any other, but when not on max, they can be 15db quieter. It sounds like you are making the right steps, but you have a bad starting point.

My AC just came on again (it is rather hot out). I opened the patio door. Even with the door open, the fan noise is louder.
 
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srrxr71

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I was expecting more wife jokes in a thread titled "Domestic Noise Suppression." ;)
Hahahaha. Sorted that problem out to my benefit and I’ll leave it at that. So now i’m just dealing with mechanical noise. Moving around the pads actually gained me 5dB.
It sounds like you have a noisy AC. The concrete does sit on dirt so you still have that mechanical isolation.

I am going to guess you have a single stage AC? I don't think they are any noisier than they were in the past.

The new variable speed units are super quiet. Most of the time they are running far below max. At max they are just as loud as any other, but when not on max, they can be 15db quieter. It sounds like you are making the right steps, but you have a bad starting point.
I think so. The previous unit failed and the owner installed this dirt cheap bottom of the line Goodman unit. I did my research and learned that higher end units come with the compressor blanket built in.

Of course the unit being within inches of the wall of my listening space is another issue. If I had any say I would have researched and bought the quietest unit.


I think the unit is also underspecified for the space so it struggles during daytime to even get to my set temperatures. During night it works great and maybe it’s the variable speed aspect that is giving me that 5dB gain. Somehow I doubt that it is a variable speed unit. It’s a decent 14 SEER unit but I think that is minimum these days. It does bother me that the 16 SEER unit is only $200 more and the owner/management company didn’t want to spend that. They don’t care what the tenant’s electric bill is but the $200 would save far more than that over 10 years.


Also it was installed in a hurry at night so it’s possible some of the pressures and charges might not be optimized. Lot’s of units failing and installers are overworked.

Can’t wait for real estate to come back to earth and get my own. I would get my listening space handled. The system is end game for me so any future expenditure comes down to acoustics and noise issues.
 
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sam_adams

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The expensive, tie-consuming, all too obvious solution is to build a three-sided concrete block sound suppression enclosure around the outdoor condenser.
 
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srrxr71

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The expensive, tie-consuming, all too obvious solution is to build a three-sided concrete block sound suppression enclosure around the outdoor condenser.
That’s actually a great idea. There are some spare concrete blocks out here. I can stack them just on the wall side and that should make the bulk of the difference. Then if there are more blocks I would put them towards the back of the house where it seems the corner of the fence seems to be amplifying the sound.
 

Hipper

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Another way of finding the problem frequencies is using Room EQ Wizard (REW) and it's Spectogram.

I get traffic noise in my room and you can see it is around 40Hz because it is already there before the REW signal starts around -200ms presumably.

S8.jpg


Ideally you not only need to know the frequencies but also how it transmits into the room - directly via the wall, perhaps through the floor or some other way.

Reducing external or ambient noise has a very real impact on how you hear music in your room and is very worth while trying to solve such issues. For my traffic problem I installed a third layer of glazing which, whilst not curing the issue at 40Hz, led to a much better listening environment - more detail audible in the songs. Here's the before and after for the addition of this glazing:

FN1N2.jpg


You can see that the region 100-1100Hz is reduced with the addition of the third layer of glazing (green).

I've no experience of HVAC but you can get material that sits under equipment like washing machines that can reduce the vibrations transmitted. Perhaps they could help with the fridge:

https://www.customaudiodirect.co.uk...ing/soundproofing-underlay-quietfloor-premium

I found Custom Audio very helpful with advice. I appreciate you are probably in the US but there must be similar companies.
 
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srrxr71

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Another way of finding the problem frequencies is using Room EQ Wizard (REW) and it's Spectogram.

I get traffic noise in my room and you can see it is around 40Hz because it is already there before the REW signal starts around -200ms presumably.

View attachment 222312

Ideally you not only need to know the frequencies but also how it transmits into the room - directly via the wall, perhaps through the floor or some other way.

Reducing external or ambient noise has a very real impact on how you hear music in your room and is very worth while trying to solve such issues. For my traffic problem I installed a third layer of glazing which, whilst not curing the issue at 40Hz, led to a much better listening environment - more detail audible in the songs. Here's the before and after for the addition of this glazing:

View attachment 222314

You can see that the region 100-1100Hz is reduced with the addition of the third layer of glazing (green).

I've no experience of HVAC but you can get material that sits under equipment like washing machines that can reduce the vibrations transmitted. Perhaps they could help with the fridge:

https://www.customaudiodirect.co.uk...ing/soundproofing-underlay-quietfloor-premium

I found Custom Audio very helpful with advice. I appreciate you are probably in the US but there must be similar companies.
Indeed I have 3 EVA pads under it now and one under the compressor inside. 4 more are coming tomorrow which I will place under the unit. Maybe I’ll try some under the fridge too.

That’s just step one. Also 2 acoustic panels are coming tomorrow. I’ll take measurements after and see what more I can do.

I like the concrete block idea also. A layer on the wall side would help at least reflect the noise energy somewhere that is not my living room.

The path the noise is taking is an interesting thing as well. I can try to use either REW with a long cord to the mic or AudioTools on iOS. Walk around and see where it’s coming from.

Sitting in my MLP I can turn my head and hear different overtones of the noise. What’s interesting is the noise is actually worse upstairs in my bedroom above the listening space as there are windows letting that noise in.

This will be a fun project. Thank you for your insights.
 
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srrxr71

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Hope someone has some answers. My furnace fan is louder than the AC, but the fridge!
I’m going try these for the fridge also. They did well under the condenser. I’ll let you know how it goes. Can’t hurt.

LBG Products Rubber Anti-Vibration Isolator Pads,Heavy Duty Blue EVA Pad for Air Conditioner,Compressors,HVAC,Treadmills etc (6'' X 6'' X 7/8'') https://a.co/d/a0pQC0w


However my gut is telling me the sound is reflecting off the back wall and getting sent all over the room. It’s very annoying.

So I think maybe placing an acoustic panel behind the fridge is the way to go.
 
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JeffS7444

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I wonder if some sort of active noise cancellation might be helpful? Say, microphone situated where it will pick up unwanted sound, perform bandwidth limiting and phase inversion, then mix back into program audio.
 
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srrxr71

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I wonder if some sort of active noise cancellation might be helpful? Say, microphone situated where it will pick up unwanted sound, perform bandwidth limiting and phase inversion, then mix back into program audio.
I suppose it could but would be dependent on the seating position. Same issue as we have for digital room correction. Now that’s a great idea for all the room correction companies to address.

I suspect this is the way of the future. With full on head tracking and measurements for multiple head orientations.

Just digital room correction has saved us thousands in acoustic treatments. The next level is domestic noise. I doubt genelec will pursue this as they assume their customers are professionals in a treated studio. The other companies focused on the domestic space could throw that in. I suspect the measurements would need to automated like how a spinning 3d scanner works.

I wonder if we would have to wear microphones behind our ears for real time correction. Otherwise I can’t see it being fully accurate and might make things worse rather than better.
 

rdenney

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Have you looked at the copper refrigerant line from the outside compressor to your house? These can be quite stiff and if attached to the house firmly can transmit a lot of vibration to the wall. The solution would be to open up the hole through which the refrigerant line passes and fill it with spray foam (not the hard, brittle kind but the softer "space-filling" type). Then, spray the outside of the foam with Flex-Seal. Butyl rubber sealant putty also works--"Coax-seal" is one brand. Probably the closed-cell foam tubing insulation noodles will also work--just do what it takes on the outside to keep the rain out. These will isolate and damp vibration transmission from the copper refrigerant line to the wall itself.

That refrigerant line really should be insulated anyway, but usually only the return line is insulated to prevent condensation from forming on it.

The refrigerant line may also be installed on the outside of the wall to some distant entry point, in which case lifting off the clamps that hold it in place and replacing them with larger clamps that will go around an insulation noodle will help with isolation.

Rick "whose air handler rings the room at 120 Hz, but without distraction" Denney
 

Hipper

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I wonder if some sort of active noise cancellation might be helpful? Say, microphone situated where it will pick up unwanted sound, perform bandwidth limiting and phase inversion, then mix back into program audio.

Wasn't there one of those boutique companies whose name escapes that made a room mode cancelling system employing a microphone and subwoofers? It made sense to me at the time but of course the price was silly.
 
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srrxr71

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Have you looked at the copper refrigerant line from the outside compressor to your house? These can be quite stiff and if attached to the house firmly can transmit a lot of vibration to the wall. The solution would be to open up the hole through which the refrigerant line passes and fill it with spray foam (not the hard, brittle kind but the softer "space-filling" type). Then, spray the outside of the foam with Flex-Seal. Butyl rubber sealant putty also works--"Coax-seal" is one brand. Probably the closed-cell foam tubing insulation noodles will also work--just do what it takes on the outside to keep the rain out. These will isolate and damp vibration transmission from the copper refrigerant line to the wall itself.

That refrigerant line really should be insulated anyway, but usually only the return line is insulated to prevent condensation from forming on it.

The refrigerant line may also be installed on the outside of the wall to some distant entry point, in which case lifting off the clamps that hold it in place and replacing them with larger clamps that will go around an insulation noodle will help with isolation.

Rick "whose air handler rings the room at 120 Hz, but without distraction" Denney
Thank you for your detailed advice. I have all those items coming and it will be my weekend project.


I also ordered a mass loaded vinyl sheet 1/8” 4’x10’. I’m thinking of placing concrete blocks against the MLV which will be against the wall. The pipes going into the wall would be the problem. I would have to leave some space for them.

I have all this stuff in order and I will figure out what they do. I guess it will be a lesson on the properties of these products.


The fridge is another thing altogether. Most of the noise comes from the compressor on the bottom and it is centered at 60Hz with an overtone at 120Hz. I guess same as any other compressor.

I think I’ll just call GIK and get advice on that. It will be funny spending almost the cost of the fridge on making it quiet. Some people say open it up and wrap the compressor in MLV. The coils are also going to vibrate as well so the wall behind will need absorption capable of taking 60hz. That looks to be 6” thick at least. Maybe just the bottom 24” would be a start.
 
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