The higher the frequency the less that mounting arrangements and sounding board damping will help - it always will help, but at higher freqs more is directly radiated, as opposed to the vibration being coupled out into a larger object that acts like an impromptu speaker cone.  Corrollary of course, really low frequencies require a very positive sound break to avoid transmission.

The origin is almost certainly a ferrite core, wound as part of a switch mode supply.  The actual main switching frequency will almost certainly be supersonic - some are in the low MHz region these days but to maximize efficiency as the load varies, the oscillations are started and stopped - in the language of the old RF sweats, 'squegging' and that stopping and starting of the ultrasound is what occurs at a rather indeterminate audio frequency.

There are various things that can be done to mitigate at the design stage - specifying a conformal coat (varnish) is one, and another is ensuring the starting is soft, or having a permanent load so it never quite stops, but both of those lower the efficiency.

As regards the screws to the wall, the  (maybe asbestos)  rawl plugs that retain them would have been hammered in with hand tools, you may find if you look at the heads, that also goes for the screws as well - not every thing was done better in the old days. And mild steel screws expand if they rust becoming surprisingly tight. Usually permanent until the board is removed, and then it is a crowbar ;-)

Mike

Thanks for the description. So my working hypothesis is that there is material in the structure of your house which is resonating in sympathy with whatever frequencies are emitted by the meter(s). They might well be undertones of what the meter is putting out. The energy to drive the resonances will be coming not just from the meter but from other structural sources. As a general phenomenon it most certainly happens. I am sensitive to it, differently sensitive at different times. I first noticed it in Germany two decades ago and hadn't noticed it in other countries where I have lived (different building structures; different mounting habits; different frequencies; different me). It has been at times mildly annoying, but not to anywhere near the extent which you describe. 

It is countered or stopped by dampening the connection between meter and house structure. As in your case it is mostly meter-to-box/board and then box/board to wall, so there are two connections one can choose to dampen. 

I suggest you remount the board with damping (not just backing on the board but also between board & mounting screws - rubber washers under the screw head, for example). I suggest further that you have the meter similarly dampingly mounted on the board. Whatever is resonating will thereby lose its input.

The workers might need some persuading - there is almost bound to be a "most people don't have this problem" response (which, reading between the lines, you seem to have encountered). To which the obvious answer is "I am not most people. I have medical reports on my tinnitus response to this phenomenon and the partial solution is to dampen the resonances."

I am no medic, and of course your tinnitus response is specific to you (trigger frequencies, etc), but I would think it highly likely that if the resonance is so dampened then your tinnitus response will be proportionately milder or, hopefully, absent. 

mapj1 said:

The higher the frequency the less that mounting arrangements and sounding board damping will help

Sure, but the undertones could well be developing in/on the board, if not in the meter housing itself. One test would be to dismount but not disconnect the meter. Then you get the "raw" meter tonal product, and can qualitatively tell whether the mounting and then building structures are amplifying it.

Thanks Peter. I'm struggling to get those old screws to turn and one of course is impeded by the meter itself. So as a temporary measure I have stuffed some thick material into the gap between the wall and the board. I accidentally found I could reduce the sound the meter is making by moving the output neutral and live cables upwards slightly, so I have put in something to wedge them up. I don't like putting pressure on any electrical cables but the thickness of these is quite substantial and the force is low. I reckon it is better than anything I could devise to put pressure on the corners of meter's plastic casing to replicate what I did with my hands. Little bit bizarre with the cables but the overall result is that the audible noise is now pretty minimal.

I now have to wait and see if there's any affect on my tinnitus. It would be amazing if it reduces for just something as simple as dampening how the meter is fitted. I won't be overly optimistic in thinking it will go altogether, I believe there are harmonics still around causing it. Acoustically, the sound analyser app on my phone shows a big improvement below 10kHz, but there is still some noise registering at 10kHz and in it's top range of 17kHz to 21kHz.

Unless I find something that really looks promising at reducing the tinnitus, I am pretty sure the energy company will not send their subcontractors back. It's a shame they not more interested in finding out what's happening here than they are. I'm hardly a great advert for smart meters at the moment and finding a solution for one of the most reported health complaints would be so beneficial on lots of counts. In the meantime, I'm having to consider further respite away from home as last night's sleep was abysmal once again. Strange head pains now as well as the tinnitus plaguing me, interesting talk with a GP coming up tomorrow. Let's see how tonight goes, I will need a couple of good sleeps at least to judge this as successful, but I'm very grateful for something that makes a difference. It's already proven I can quell that rotten audible noise, which has been an irritant to my tinnitus if nothing else whenever I've needed to go into the understairs cupboard.

I live in a different regulatory regime, and I guess it is histories like yours which make me grateful. An electrician is supplied with a calibrated meter if he/she asks the supplier. The meter is installed by the electrician, and registered with the supplier (to each meter there is an account with a named user). If there is a problem with the installation, I call my electrician and he fixes it. There is "what do you want to do *that* for?" and "if you really want that, I'll do it, but I don't see the point" and suchlike, but the bottom line is that, after minimal but pertinent discussion, if I want something, it gets done, and it gets done the way I want it. With an opinion, gratis. What he probably can't do is reinstall electromechanical meters, because the supplier isn't issuing them. But remounting a box the way I want it is no problem. 

One current issue is deciding whether I want to install Type B RCDs on all circuits. I have an older house with wooden floor constructions which host a certain number of critters who don't pay any rent and like to chew cables, mice and martens. I am somewhat concerned about arc faults sending me up in flames (I have been concerned professionally about this ever since TWA800 in 1996, when arc fault circuit breakers were novel and 20+ times the price if you could get them). It hasn't happened yet but the critters aren't going away. 

If I were to be as concerned about the hum in my place as I was two decades ago, I could have it fixed in a day. But I am not. In the last couple weeks, the population of my city has increased 1% with people who have been bombed out of their homes. That is likely to go up considerably. There were some 90 orphans on the way to us in buses .... that just disappeared from the face of the earth before they even got to Poland. We have a lot more to worry about than hums in buildings.

yes - I'm not saying it is not worth trying to damp it more that higher freqs benefit from enclosures to trap them and low one from something more like shock absorbers to mechanically de-couple them.

There are anti-vibration pipe/ cable clips made to decouple cables and pipes from vibration in a dissipative way

This sort of thing  a stack of washers betwen it and the board to avoid too much strain.  That  is an image of the sort of thing but  i expect for small quantities then Ebay may be your friend ' padded P clip' or 'cushion P clip' are the right sort of search terms.

Take great  care with anything that might  move the meter board - depending on the state of the incoming cable it can go very badly wrong if it  drops off the wall and kinks the cable incomer sharply. Older lead covered paper insulated cables are very unforgiving of that sort of abuse, and of course the company cables are on the wrong side of the incoming fuse, so the potential for arc flash injury in the form of something more than an instant sun-tan is much higher than after the meter. (so do not go mad and pull it about like a gorrilla.)

Mike.

Hi Mike, thanks for the tips on this.The house has been rewired around 30 years ago so the cables are a little bit more modern than what you descibe and I have been very gentle with them. It was suprising just how much difference it made to the audible meter noise which I am glad to quieten down, but I don't think, certainly not from how I feel at the moment, it is going to affect the tinnitus much.

I do wish it was as simple as calling in an electrician to install a different meter, instead I'm at the mercy of the energy company who do not believe anything is wrong with their meter. The energy market at the moment is virtually broken here in the UK, to the extent switching companies is very difficult and expensive as companies do not want new customers. If they offer tariffs for new customers they are double or even triple the government capped variable rate. Then I have the problem of asking them to change the meter. I've already been refused on the grounds that it wasn't for the next company to resolve a problem with a meter installed by the previous company.

Tinnitus is not like building hum. If there's a link between the amount of audible noise the meter makes and the tinnitus then hopefully the changes I made today will make a difference. While I am certainly glad that the audible noise is now much reduced, I can't report any reduction in the tinnitus yet. Indeed I won't know for several days as it is taking longer and longer for my tinnitus to fade even when I leave my home for a several days as per last week. The tone I'm suffering remains loud and clear at around 14kHz, earplugs only make matters worse as they cut out all other sound leaving me to hear nothing but the tone. Tinnitus leads to insomnia, headaches and fatigue all of which I'm now suffering to a large extent, all of which lead on to other health issues. I'm worrying about the long term effects of all this too. While I'm much more fortunate than the people being bombed out of their homes and losing their lives in Ukraine, I feel as if I am losing my home and I just can't live with the tinnitus I am suffering here too much longer. No one should be made to feel ill from the installation of any electrical device in their home, particularly one that they cannot turn off and replace.

I'll confirm after another torrid night, that dampening the audible noise the meter makes has had no effect on my tinnitus. Sleep has been limited to between 4 and 5 hours broken into 2 parts. I really do need this problem solved quickly. Evidence for my case with the Ombudsman closes tomorrow. I'm hoping for a speedy adjudiciation with it being a health matter, otherwise I could have several more months of this, which put simply, is not possible.

That is a pity - the audible thing you have suppressed is clearly not the whole story, though it does suggest the whole thing was vibrating as a sounding board for the audible part of things and that has now been nobbled. But for you there is more going on, and personally I'm not sure what to suggest.

In general terms, anything radiated from a point source will go down as the square of the distance, so you should be a hell of a lot worse at 1m than at 5m.  If something is ducted / guided then it becomes the unexpected transmission line you need to get away from of course, which could be the wiring, but is unlikely. 
How good is long and medium wave reception in your building?, that can sometimes be used as the canary in the coal mine as the AM is very good at revealing sources of RF noise.

Mike.