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Not thinking of any active correction, but first to identify what it is, and if it is the roof resonating I thought if I could shift the resonant frequency of the roof by adding weight maybe to some of the beams, then it might move away from whatever vibration is coming from the farm and reduce the effect. Or construct a tuned mass damper like I linked in earlier post to target the 20.52Hz resonance. That's a mass and spring system tuned I think to have the same resonant frequency, but with a damper attached. Mostly they seem to be on a much larger scale though (bridges, skycrapers etc.)

This weekend I found time to record with a condenser mic. With the mic in the stand I didn't see much, but with the mic lightly touching the wall I am able to see a difference between when the hum was there in the morning, and later in the day when it's gone. Orange line is power recorded for different frequencies when I could hear the hum, yellow line is same setup but later in the day when the hum was off. The blue line is a control with the mic off to see the line noise in the laptop and audio interface. Looks like there are two things there, a tight frequency around 20.5 + harmonics up to 102.5 (5 x 20.5) and also some peaks at 47 and 49 Hz. I suspect the thing around 30Hz is fridges and freezers as it appears in both conditions. I could try this with the electricity in the house off as recording on a laptop with a USB interface. I think 20.5 is certainly in the ball park for resonant frequency of a pitched roof and I think mechanical resonance induces harmonics so that's still the best guess. Will try a longer recording (this was based on 1 minute) to try to pin down the frequency as accurately as possible. Best I get from this (using a longer analysis window is 20.52Hz). I found this: Just a moment... WWW.RESEARCHGATE.NET So crudely interpolating to say a height of 4.5m would give a 1st mode of 20.3Hz and second mode of 48.5Hz. So I'm thinking the stuff around 47/49 could be the 2nd mode of the roof.

Thanks for the suggestions! If I can confirm it is coming from the farm then like I said I think it is to do with the roof resonating because we don't hear it outside. So I would look to change the resonant frequency of the roof by maybe hanging some sandbags off rafters, piling some insulation in the corners or against the gable ends to change the major mode of the space. Any other ideas along those lines welcome! Actually this looks like what I need if I could accurately measure the frequency and build something that matches. Tuned mass damper - Wikipedia EN.M.WIKIPEDIA.ORG Haven't been able to pick out the frequency. I have a good condenser microphone but I don't think it has sensitivity at 50hz or below (have a feeling the roof might be around 25, so the 50hz power hum might be matching the first harmonic). Thanks again for everyones input, has been really useful and also entertaining.

Thanks a lot, I think we have a winner (or at least current top candidate). Will keep an eye out next spring for cows in the field to see if it stops with that. But I think that explains the seasonality. Still not completely sure why the timing would be as it is (perhaps off peak?) but it does sometimes run in the day, and it does sometimes skip days or go a good few days without hearing it at all, but perhaps that could be atmospheric differences. But otherwise slurry system when the cows are in fits the bill.

Frequency and intensity doesn't change (just these 1-2s pauses every 20s - 1m, but that could be psychophysical). Not sure what frequency but will try to find out. I think the cows do go into sheds around October, so perhaps related to that only just realised that they have disappeared from the fields around the same time. But what related to cattle sheds would only go on at night? We only have access to one external wall, the rest is terraced or other peoples land so a bit dificult to do anything. It does seem to be coming from the west, but just connect to another house. It's not intolerable, mainly I think I would feel better knowing what it is, but impossible to sell and move at the moment (mortgage rate would more than triple, have put a lot into the house already). If it is resonance of the roof maybe it could be mitigated by hanging weights or putting more insulation. I am looking into renting a seismograph or other recording equipment but seems a bit expensive even just to rent for a week.

Thanks all for the responses! - tinnitus / it's me: I have checked with my wife and she hears it (and doesn't normally put up with my nonsense), but it doesn't bother her as much. Also a neighbour hears it, but only on one side. It does seem like a vibration rather than a noise so not sure about the water pipes, also its more apparent upstairs, while our mains water comes in downstairs but I will check the pipes over the next few nights. Also why it would have the clear timing and seasonality. - agricultural tips are useful, grain store, agitator. If it is something coming from further away then I think it is coming through the ground and resonating the roof of our house becasue only hear it inside. This is my best guess of what is happening. - weed farm. I think its unlikely, the neighbourhood here is so nosy I am sure we would have heard about it (we heard about a small scale medical grow operation the previous owners had going in the attic of our house). - electricity: no substation but we do have a transformer up a pole for this little hamlet. Again not sure why it would have the timing, other neighbours have suggested BT phone pole, there is one close but I don't think theres anything powered on the phone mast and again timing / seasonality doesn't fit. - sewage is a local large septic tank (12 properties) draining out to a reed bed. I don't think there is anything mechanical involed. - one house a few away has a heat pump but I thought they run all the time. Will definitely investigate this. - milking, was suggested by another neighbour who commented they sometime see large trucks from the milk company arriving around that time of night (10:30 or so). "i usually cup my ears with my hands to get a bearing on spurious sounds...take it one step further, a decent directional microphone.." I've tried this but not possible to hear it outside, as above I think its a vibration resonating the roof. I tried touching walls and stuff but the only place I can hear it really is inside our house, even just sticking my head out of a large velux window I can't hear it outside. - wind farm, there is a samll private turbine on one of the farms, maybe 1-2km away. Large scale wind farms are visible on the horizon, but I'd say 10 miles or so. Again hard to see how it fits the pattern of timing / seasonality, doesn't seem related to wind. - power cuts, will definitely keep an eye out, but haven't had one long enough when we are in. That's why I thought I might ask the neighbours to turn their electric off to test one at a time. I guess I will try to start keeping a log of the actual times its on to build up more of a picture and try to catch it turning on and off. Other guesses I had myself were somethign to do with heating in the stables or something else for horse care, or a neighbours surround sound system that has a noisy input that makes a hum when the TV is off (idea was the noise starts when they turn off to go to bed). But I don't think they run their TV during the day and doesn't fit the seasonality (unless perhaps its caused by electrical noise connected to their heating system, but the boiler and stuff is the other end of the house from the tv, there property is mirror image of ours so I know the layout). I've asked all the neighbours though with no ideas (they have checked their heating and so on). Attached are some higher resolution images of the closest farms. There's certainly milking and slurry.

Could be, would it be posssible to tell from the satellite image? There is definitely no grain growing anywhere nearby, but there could be a store for feed? This is a useful tip though thanks I know nothing about farming so had no idea what it could be.

No, its definitely real, my wife can hear it when I prompt her (but it bothers her less than me), and our neighbour in the house to the west has also heard it since they moved in - they think it is coming from the farm. They don't hear it in the mornings, but report it starting as night, not hearing outside, etc. same as us. It's definitely not ours - the existing combi boiler failed last Christmas and have a whole new system in January with no difference to the noise. Switching off power at our fusebox cuts off everything. It could be neighbours heating, but why would a circulartion pump be on all night every night from October, it would be controlled by a thermostat and also on during the day? There is a stables attached to a larger house in the hamlet, so I did wonder if it could be something to do with heating the stables, but again not sure why it would be on all night. Thanks for hte thoughts though.

Hi all, Got a lot of useful help on here for a flue so thought I would ask if anyone has any ideas for this. Moved into a new house last April. It's a farm / barn conversion done around 2004, around 15 other properties in the farm. Terraced, with other properties both sides. Quite rural in Ayrshire, local farming is cows + sheep. There is a low level hum / vibration that I can't identify and it's driving me crazy. When on it is constant low level hum, I think its resonating with our roof because it's louder upstairs. Same volume both ends of the house. It's on constant with maybe 1second pauses randomly every 20s-1m. I don't hear it at all over the summer, both last year and this year it started within a week of now (last week of October). It tends to start after 10:30pm at night, hear it less during the day but do sometimes. I thought it used to stop earlier but this year I am still hearing it now (9:30) and later into the morning. I haven't been able to tell if it stops suddenly in the morning or winds down (getting quieter). I have eliminated everything in my house by turning off the electricity at source (and having an old meter that was buzzing changed for a new silent smart meter). The usage pattern rules out any of my first thoughts (freezer compressor, bathroom extractor fan etc.). I thought it might be off peak electric heating - two properties that we have a physical connection to are heated with electricity, but I have spoken to them and they say there is nothing off peak, and their off peak hours skip 12:30 - 4:30am etc. when we still hear it. Certainly this year it seems to be going a bit later in the morning, also this week when the weather is very mild, so doesn't seem to be connected to outside temperature apart from starting at the end of October. One other house reports hearing it and they think it comes from a farm to the west. It's strange to me as it's impossible to hear outside, but maybe it is coming through the ground and interacting with our roof. There are no farms close by, would be 1-2km away. Does anyone have any ideas of what it could be, or what I could do next? All I can think to try is eliminate a local source by asking neighbours to turn off their electricity at the meter while it is on. But this is a bit difficult because of the awkward hours its on and I'm not sure they will do it. It is not loud, but it goes straight through ear plugs and I have a sensitivity to noises so it does bother me. I've contacted the council which might take some time, but I suspect if they came to measure anything it would not cross any defined noise level threshold for nuisance. We also had a problem where all our pushfit plumbing came apart - the pushfit fittings had unscrewed which the plumbers had never seen before (they are never supposed to unscrew, they are just pushed in) and I wonder if years of this low level vibration might have caused them to work loose. Any thoughts of anything that it might be would be great, or things to suggest. Reading online about dairy farms the only thing I could find that would make a nuisance was an external milk chiller, but this doesn't match the winter schedule or the continuous pattern (ie not a compressor going on and off under thermostatic control). If it is coming from farm or agriculture here is a satellite image, we are in the right-most hamlet of the image and all of the things to the west are farms.

This is the air filter we have: 503 - Service Unavailable Error WWW.AMAZON.CO.UK (although it's now more than twice the price I paid a few years ago). The other eye opening thing was how much the PM2.5 level increases with cooking, frying, but even having something in the oven.

Updating here in case it helps anyone in the future. It was Poujoulat! They were able to identify the photo and were very helpful. It was actually an older 155mm flue that they made up until around 2004/2005, so I needed a 155 to 150 adaptor, and a new 150mm extension. They do different lengths, 950mm and 1150mm which worked out well because 1150mm plus around 50mm from the adaptor takes me close to the regulation height (2.3m horizontally from roof) with only one join (and total height above roof not enough to require a support according to the specs). Hope it will stand up to the storms. This was £320 for the two pieces. Was really happy to have it finally solved, but as proof of the old saying no good deed goes unpunished the lady of the house who originally complained about the flue and asked us to increase it to meet regulations as they are bothered by smoke came round 10 minutes after the job was done furious about how it looked. Not quite sure what they want us to do. We need access through their garden so they had advance warning of all the details. I think she wants us to paint it black? but feel a bit agreived having gone to all this trouble and spent 600 quid all in to be good neighbours and fix their smoke problem at their request (fluecube alone would have sorted our our problem) only to have it thrown back in our face. First time living in the countryside and frankly amazed at the level of entitlement. We've been here less than a year, the stove has been there 18 years but the woman was raging at us that "they never gave permission for it's installation" (of course none was needed).

Update: the convesa didn't fit, so we have just put the fluecube on. Here are some pictures of inside the existing piece. Any other suggestions for a make to try based on these (the sort of end grills?) The internal here is 6 1/4 " rather than the tight 6" of the Convesa. I've had a suggestion it is likely to be Poujoulat, but not sure which system or where I can buy a 1m Poujoulat piece, any help appreciated.

Thanks, yes I checked that and I think as long its just a 1m extension piece I should be comfortably under the limit for KC (assuming that KC / TWPro / Convesa are all the same product): "Locking bands are included with each component as required; the standard locking band will provide lateral support for up to 1.9 metres of pipe above the final wall support. Structural locking bands are available and allow an additional metre height." I estimate whats on there is around 0.5m so witha nother 1m should be fine. Also looking at the neighbours almost all are more than 1.5m and none have bracing. I think I would need to add another 0.5m to ensure full compliance with regs, but then I think I would need the supports to be safe and want to avoid anything that could compromise the roof given that when it comes to this house, anything that can go wrong will go wrong. I think a 1m extension will take it 1m about the windows and be an obvious improvment for the neighbours with cleaner burning provided by the fluecube I think that would be a good outcome. Compared to the price of new flue actually I could by a 1m section from all of the candidates (although seems like its not selkirk now, but could get an Sflue alongside KC flue) just to be safe that I have one that goes on. Thanks again,

OK thanks. Looks like that convesa KC / TWPro (seems to be the same product) 1m pipe is the best thing to try and not so expensive. Thanks very much for the input I would have made no progress at all without the help in this thread.

OK, so I guess the message is it is a bit difficult to identify? Does KC stand for anything, I cannot find much online searching for that? Would it be this? (KWPro the same as KC?) KW Pro Twin Wall Flue - 175mm - 1000mm Length WWW.FLUESYSTEMS.COM KW Pro is a twin wall insulated chimney flue system designed for use with stoves and fireplaces which are burning wood, solid fuel, gas or oil. 175mm Diameter. 1000mm Length Now have a quote for installing a new flue for £1650+VAT which is more than I was expecting but it seems to be the only option short of waiting until 2023. What about this one: 1000mm Stainless Twin Wall Insulated Flue Pipe – 6 inch Convesa – Modern Stoves – Contemporary Multi Fuel Wood Burning Stove Specialist WWW.MODERNSTOVES.CO.UK Fixed length: 1000mm - Effective Length When Joined 962mm Internal Diameter: 150mm (6 inches) External Diameter 210mm HETAS Certified - CE Approved Colour: Stainless Steel Mirror Finish Please note that we sell... Looks pretty close based on the band (and it says KC at the bottom of the listing). Might be worth trying that and a fluecube if I could get someone to put it on?