Anybody know about chimneys? Antennas? Insulation? Calling all builders, etc.

diamdave

diamdave

Joined
Nov 29, 2001
Messages
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We have a brick chimney in our circa 1956 Georgian. No fireplace. Some time ago I asked about possible solutions to our 'hum', a resonance of some
45-55 hz that occurs in our home for a few days, then subsides somewhat, then returns. Neither fans nor sound machines nor earplugs help... too low.

(...and yes, I got my hearing checked just to make sure I didn't have tinnitus.)

We've ruled out electric power, gas line, dryer vents, hot water tank, kitchen vents, etc. We don't have an attic fan. Nearby factories could be possible source, but neighbors don't hear it in their home, (we are on a corner,) and I can't shut down a factory anyway.

Hum is noticably more prominent when wind is South or SWS, much quieter when east or NE.

Our gutters seem tight. Roof is new and this started long before we put it on.

We have a cap on our chimney, and people tell us that homes our age used clay liners, not metal ones. The chimney runs behind our main bedroom closet... that back closet wall sounds hollow when you knock it, compared to other walls in our home.

Could wind somehow be blowing across and causing a low hum? Could the factory sounds be vibrating something in a chimney? Antennae? Cap is tight, can it still vibrate?
Sounds like a truck idling outside, but when you go outside its quiet.

Also, we have an antennae on our roof... anybody EVER hear of an antenna conducting low noise into a home?

One person suggested shooting non-flammable insulation behind our closet wall and the chimney, thinking it might break up any sound waves...insulation places wanted $600 just to come out, etc. Not viable.

I went into our attic. We have two toilet stacks, and two roof vents. The vents don't seem to be vibrating. You just hear a little outside noise as one would expect.. that's what vents do, open to the outside.

Sound is heard throughout house, but often more noticable, of course, when sleeping. Hear it more in closets. Wakes me up. Windows upstairs are new.

I'm open to all constructive suggestions... thanks.
 
It's haunted! Move now!

From what I have read and seen in the fire service it is possible that wind is blowing across your chimney or roof vent pipes. But if there is no wind blowing..well, you know...no noise. Clay lined chimneys, especially old ones, have a tendency to seperate from the brick. If wind gets in between the liner and the chimney itself it could make a sound that would fill the house. And being that it is hollow behind the wall near the chimney it is resonating.

From what I know and experienced this may be the problem but anything is possible.
 
Last night the wind was 4 miles per hour from the South (Weather CHannel)
Sometimes with a strong wind, say 20-30, it's actually quieter. I didn't know that clay liners can seperate from the chimney though.
 
I have never heard a chimney hum at that high a frequency. But the frequency you cite is still so low that only mass dampens it in walls, no reasonable thickness of any light weight insulation is going to help, thick gypsum board is the easiest solution if it is a solution at all.

Block the chimney at top and see what happens.

TLM
 
yes what he said block the top of the chimney and if its still there wrap some painters plastic all around chimney and let us know if it went away.
 
It's much lower than 55 hz, my bad. Maybe 35-40. Hard to tell without measuring it. I'm going to try and borrow my neighbor's ladder to get way up there and see if covering it changes anything. With the heat turned off, of course. Don't know where else to turn.
 
If it's a column of air that's vibrating (and not an antenna or something) and it's 35 hertz it's about 31 feet long, or if it's 40 hertz it's about 27 feet. It's not necessarily straight -- I doubt it's folded up like a trumpet but it could be an L. If you can do anything to shorten the column of air the pitch will be raised and that will show you've found the source.

You probably knew all that anyway....

Wait -- that's assuming the column is open at both ends. If it's closed at one end (like a clarinet) then it's half the length for the same pitch.
 
More likely to be the open top toilet vent stacks. There is one daft way you can try and find the direction of the noise. Close one ear and put a plastic funnel in the other. It will concentrate the direction of the noise. You can also use it as a stethescope for listening to walls, closets, chimney breasts etc.

Other than that, wait until you hear the noise, get a ladder out and stuff rag in the chimney and stacks one at a time and see if the noise stops.
 
I emailed your entire post to a buddy of mine who is the Yoda of chimneys. (He sets the exam which professional sweeps have to sit in order to become qualified).

Here's his reply, interleaved with your post:

Sure thing I'll comment in red. This is ringing bells in the back of my mind. I am certain I have read of a similar case, possibly in New Scientist. Tell the guy to go to their site http://www.newscientist.com/home.ns and see if there is a reference. Try the questions page at the back of the magazine.

"Anybody know about chimneys? Antennas? Insulation? Calling all builders, etc.

--------------------------------------------------------------------------------

We have a brick chimney in our circa 1956 Georgian. No fireplace. Some time ago I asked about possible solutions to our 'hum', a resonance of some
45-55 hz that occurs in our home for a few days, then subsides somewhat, then returns. Neither fans nor sound machines nor earplugs help... too low.

(...and yes, I got my hearing checked just to make sure I didn't have tinnitus.)

We've ruled out electric power, gas line, dryer vents, hot water tank, kitchen vents, etc. We don't have an attic fan. Nearby factories could be possible source, but neighbors don't hear it in their home, (we are on a corner,) and I can't shut down a factory anyway.

Hum is noticably more prominent when wind is South or SWS, much quieter when east or NE.

Our gutters seem tight. Roof is new and this started long before we put it on.

We have a cap on our chimney, and people tell us that homes our age used clay liners, not metal ones.

No. Houses pre '65 are brick tubes lined with mortar. Usually square, 9" x 9"

The chimney runs behind our main bedroom closet... that back closet wall sounds hollow when you knock it, compared to other walls in our home.

Could wind somehow be blowing across and causing a low hum?

Could be. Or could be the antenna, or even the cap. If the cap were slack, it would IMO be less likely to vibrate.

Could the factory sounds be vibrating something in a chimney? Antennae? Cap is tight, can it still vibrate?
Sounds like a truck idling outside, but when you go outside its quiet.

Also, we have an antennae on our roof... anybody EVER hear of an antenna conducting low noise into a home?

One person suggested shooting non-flammable insulation behind our closet wall and the chimney, thinking it might break up any sound waves...insulation places wanted $600 just to come out, etc. Not viable.

Equally could block off the bottom of the flue and fill the flue with vermiculite.

I went into our attic. We have two toilet stacks, and two roof vents. The vents don't seem to be vibrating. You just hear a little outside noise as one would expect.. that's what vents do, open to the outside.

Sound is heard throughout house, but often more noticable, of course, when sleeping. Hear it more in closets. Wakes me up. Windows upstairs are new.

I'm open to all constructive suggestions... thanks."

maximus otter
 
I'll look up that article. THANK YOU! Thanks to everybody. Any other ideas, please let me know.
 
Update:

Had my roofer who was in the area come out to see if we could pinpoint it. (Great guy, wouldn't take money for it!) He and his son checked the antenna and vents, they are all tight. Wrapped an old blanket around the chimney top as well as the toilet stacks. Still heard the sound.

This is getting weird. Also looked into the toilet stacks and said all looked clear. He felt that the antenna was not conducting the noise, offered to take it off, but said he was pretty sure the noise wasn't coming from or via the antenna.

All I've learned so far is that the low drone is louder in corners (not by much, but some) and in an empty closet next to the chimney. Roofer took off the cap, looked into the chimney, said that it was strange, that the flue only went part way down, then just stopped. Usually they go down farther.
I have a chimney guy he is supposed to come out 11/29 to see....

We also noticed that on our second floor, the ceiling bends down a the left and right ends of that floor, sort of like a barn look. Ceiling drops (concave?) maybe 6-7 inches or so. Not at an angle like a church cathedral, but flat over and then rounds down at the outside wall(s). Maybe that is conducting low frequency waves, standing waves, etc.... anyone?

Only other thing is possibly to shoot insulation inside my outside walls or behind that closet wall next to the chimney. What I don't know is if that will help if the sound was heard with a blanket around the chimney cap....?
 
Diamdave-- Do you have an awning frame that is connected to the house?

If so, this is probably the culprit. Anything metal that extends considerably from the house, with or without the sail effect (removal of awning), would produce those types of humming.
 
komondor:
Interesting... not an awning, but we have... sort of an overhang in the front of the house. It is a structure... let me see if I can find a pic for you...

Look behind the green bush... our door is on the right somewhat hidden. That red above, not an awning, more of an overhang I guess. The bottom of it is like a corrugated aluminum or sheet metal, don't know exactly. Does this give you any clues at all? Thank you.... (Ignore For Sale sign, pic is from when we first bought the house 4 years ago.)

Also, note chimney on left side of house. Window in front of chimney is our bedroom. Window on left of the front of house as you look at it is also our bedroom. Sound is everywhere, although I often think it is coming from the front of the house (which faces South) hence my interest in your awning comment.
 
One question........where is your boiler or hot water heater in relationship to your chimney and bedroom? It is possible that the sound of those items working are reverberating through the chimney. Try turning them off and see what happens. This happens in my home when the heater kicks on. It sits next to the chimney and causes it to reverb like I hit an open E on my bass and I have the amp up to 11.
 
thanks. We thought about that. The hot water tank is three years old, replaced when we moved in (AO Smith) it doesn't seem to rumble or make any noise, even though they are close together in the basement. (We have no fireplace). The thing is.. we can also hear it when neither the furnace nor the a/c is running. The drone or hum seems louder with temps in the 40-60 farenheit range, which makes me wonder if it is some kind of metal resonance. I've never heard of an overhang doing that, but then again I don't know much about home construction.
 
If the noice starts from a vibrating part putting some dead weight (like a small sand bag) on it will dampen it considerably, that's one way to test for the source. I see no mechanism how temperature could by itself make the noice.

TLM
 
Hey Guys...

Dave...

Not to make light of your situation or anything..
It must be a Drag and very annoying to you...

I'd love the challenge of trying to figure out something like this....

If the obvious has been looked at,,start looking at the not so obvious..Could be Anything really..

A loose piece of trim somewhere, flashing, loose piece of siding, something sticking out....Even a hole or crack somewhere...

I don't know,, but it would for sure be a challenge to figure out...

Best of luck..

ttyle

Eric
O/ST
 
I've got a chimney guy coming out.... my roofer noticed that the flue doesn't descend very far, he said its goes a bit, then there is just air down there. Strange. Maybe something is loose in there. Often the noise is louder with winds 5-10 mph rather than real gusty, so I don't know if that automatically excludes the chimney or not. We have a cap, but that is mostly to keep out animals, I'm told. All your advice is welcome, it's the strangest thing.....

THanks, any more ideas, I'm open.... dave
 
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