Unidentified noise in party wall

[shrewmouse]

Hi 🙂 Please can anyone help to identify this noise in the wall between me and my neighbour? Complicated but will try to explain.
It occurs every few (7 - 10?) weeks, when it does it's very regular, every 21 mins plus a few seconds.. it's like a donkey - "squeak honk".. varies in volume. Continues for a few days like that, then stops. Sound file attached. Is this familiar to anyone??
It's only audible upstairs, in my bedroom. The noise emanates from a specific place within the area of next door's chimney breast as it goes up between our walls. On the other side of that is her bathroom but nothing can be heard on her side upstairs in that area.
There is no plumbing in my house near that wall (except downstairs in my bathroom below, short length of pipe direct from the mains entry, along the wall at floor level until running upwards just behind some tiles to my electric shower unit) and nothing can be heard in that area.
My own water supply upstairs is limited to a roof tank and a basically unused water heating tank in the bedroom but these pipes go up through the centre of the house and the noise is definitely not coming from them. No pipes in the floor upstairs.
I have no central heating.
These are very old cottages. Downstairs, next door has a cloakroom at the front where water pipes enter her house. This area used to house an old fireplace, and her chimney breast still exists there. The pipes appear to enter and then run along the base of the blocked off fireplace, before continuing around a small corner and into the kitchen behind cupboards, up a wall and thence around the house. Her bathroom is above but as far as i know the water and heating pipes approach that from a different direction via the stairs and do not run along the party wall - apart from that initial area downstairs within the old fireplace area.
I've turned off and drained my entire water system, to no avail. Apparently she is unable to try that herself because it would mean resetting the oil fired central heating system.
(My feeling is it may be something to do with a build up of pressure releasing regularly or a valve of some sort, in the fireplace/chimney area? But i admit to zero understanding of these things. I haven't been round again to ask to listen downstairs in that area although we did listen upstairs to no avail. She says she's noticed nothing. If i only had some idea of the cause it might be something to approach her with again).
This is driving me mad because being by my bed i am unable to sleep in my bedroom when it is occurring. And i can't pay for someone to come and investigate someone else's system so i'm at a loss what to do. Would really appreciate your thoughts on it? Thank you for your patience if you have read through all this
Cath

 

[Chuck]

First on my list of possible sources would be a gas meter or its pressure regulator. The noise will probably happen either when a relatively small amount of gas is being consumed (or leaked) or the pressure in the (high pressure) mains side is rising causing the regulator valve to 'burp'.

Pipework transmits noise remarkably well. Don't assume that the place where it seems to be loudest is the location of the root cause.

The gas company own and are responsible for the meter so if this seems to be the problem call them rather than your own plumber.

 

[shrewmouse]

First on my list of possible sources would be a gas meter or its pressure regulator. The noise will probably happen either when a relatively small amount of gas is being consumed (or leaked) or the pressure in the (high pressure) mains side is rising causing the regulator valve to 'burp'.

Pipework transmits noise remarkably well. Don't assume that the place where it seems to be loudest is the location of the root cause.

The gas company own and are responsible for the meter so if this seems to be the problem call them rather than your own plumber.

Hi Chuck, thank you for responding. There is no gas mains here. Next door's heating system is oil fired radiators. I have no central heating at all.

I do feel it could be something like you describe but to do with either next door's heating system or her water supply?

 

[Chuck]

Could it be a bird/animal in your roof/chimney space? IIRC, there's a type of owl that sounds a bit like your recording and squirrels can make about a dozen different noises.

 

[shrewmouse]

Could it be a bird/animal in your roof/chimney space? IIRC, there's a type of owl that sounds a bit like your recording and squirrels can make about a dozen different noises.

No, it's too regular. Every 21 mins approx, without fail.
It can't be my side since I have twice turned off and totally drained my entire water system to no avail.
Next door has a more complicated set up involving the oil fired CH. I imagine this would include some sort of pressure regulator valve of the type you mentioned? If so, what do you think could be the problem with it?
Really appreciate your help Chuck.

 

[Chuck]

Okay, I missed the 21 minutes, in which case...

The 'standard' setting for a room thermostat that controls an oil boiler will make it perform a maximum of 3 on-off cycles per hour. In cold weather the boiler might be on continuously, in warm weather it might be off continuously but between those extremes it will ignite burn and then shut down every 20 minutes or so.

I suppose that the '21 minutes' could be a coincidence but in the absence of better ideas, I'll redirect the finger of suspicion so it points at your neighbour's boiler. There might also be electromechanical 'zone valves' attached at various points. These will also open and close as the boiler starts and stops but the noise on the recording doesn't sound much like these to me.

On the other hand, I thought the noise sounded like an owl, so what do I know?

 

[shrewmouse]

Okay, I missed the 21 minutes, in which case...

The 'standard' setting for a room thermostat that controls an oil boiler will make it perform a maximum of 3 on-off cycles per hour. In cold weather the boiler might be on continuously, in warm weather it might be off continuously but between those extremes it will ignite burn and then shut down every 20 minutes or so.

I suppose that the '21 minutes' could be a coincidence but in the absence of better ideas, I'll redirect the finger of suspicion so it points at your neighbour's boiler. There might also be electromechanical 'zone valves' attached at various points. These will also open and close as the boiler starts and stops but the noise on the recording doesn't sound much like these to me.

On the other hand, I thought the noise sounded like an owl, so what do I know?

Ok thank you Chuck, yes it does a bit 😆
That's interesting about the timing and maybe gives me something to approach her with again, at least. I guess the boiler might be on year round for hot water..
The boiler seems to be located on an external wall on the far side of her house, so the noise would have a fair way to travel before showing up in my bedroom. If it is emanating from that, any thoughts as to the cause?