Cheapest Way to Shield a Wall Against EMI

Oh this site made me smile. Everything you could possibly need, some of it actually looks useful. My cats would love it if I brought any of this stuff home.

Before you do buy anything HeadsUp check the site at night carefully, it may very well be sound or vibrations being transmitted through the wall that are interfering with the persons sleep, in which case an expensive EMI shield may not help.

Superb :-) Thankyou

Very cool products! GA!

First, this is not EMI.

Emi is high frequency radiation, not ac power operating at 50/60Hz.

There must be more to the story.

Maybe a 50/60 cycle hum from the mains?

Would EMR be more accurate ? And yes the hum could be it too I recall a similar case where a refrigerator adjacent to a child's bed was found to be the culprit , it did literally hum and drive people up the wall She says she feels hot headed , irritated and has mild headaches by the morning , but that could be due to the loss of sleep

I would venture a doubt as to whether a domestic switchboard could generate a field of 2-5 kV/m on the other side of the wall.

Here's the problem with this.

The fields are nowhere near those field strengths from a switchboard and mains in or around a dwelling. When we test equipment for radiated susceptibility (RS103) to MIL-STD-461, the field strength is 200 V/m and you are not permitted in the shielded room when the test is conducted because of the potential danger. At those field strengths (200 V/m) there is a good chance you will damage electronics if they are not properly shielded and protected. We know this from experience, even equipment designed for the environment can be damaged.

For comparison purposes, in the civilian world, for radiated susceptibility compliance of the IEC-61000-4-3 Class 3 (severe EM radiation environment) the limits are 10 V/m over the bands 26 MHz to 1 GHz.

If I were the building owner, I would hire "experts" to come in, use a contact cement to cover the entire wall with wide sheets of restaurant quality wide aluminum foil. Make sure you overlap the seams at least 5 cm to prevent 'leaks'.

Then run a braided copper strap into a new metal electrical box in another wall. It doesn't have to connect to anything, it just has to look good. Then cover the foil covered wall with another layer of drywall or whatever wall board system you are using, paint, and you are done.

The placebo effect can work quite well.

I remember an instrument company that put a red pushbotton on their rack-mount controllers.

Only the technician was allowed to pull the rack out,and when a problem was

reported,for which appeared to be a "ghost",not a real problem, the operator watched

the tech push the red "reset" button,and the problem ususally never reappeared.

The button had no contacts,and did nothing at all,except mollify the operator.

Mind over matter.

Tell the man of the house that he's lucky...My wife tells me regularly that she has a headache when we go to bed.

Seriously though, it could be related to this

This Wikipedia article discusses it too.

This is so strange - tell them I've always felt better when exposed to 60Hz radiation for an extended period. When I was much younger, and until it was suggested that there may be a cancer link, I would look for high voltage power lines and stand under them. Used to love to stand in plant power distribution rooms too.

Yeah - I may be a bit off too.

If the real culprit is a hum, have an electrician re-mount the main switchboard using some vibration-damping pads or grommets. Put some vibration-damping pads under the bedposts, too. If the room has a hard floor, add a thick rug and heavy drapes to help absorb sound. Then add an air purifying unit that generates pleasant white noise while it scrubs the air clean.

Air Purifier

Vibration Pads

2 x LOL!!!

Beat me to it, I was going to suggest a tinfoil nightcap, with a long cone and a big, poofy pompom at the end.

I am surprised that there is a lack of reaserch into the hazards of tinfoil hats, especially during electrical storms. If there had been, then my lucrative "Lucky Golf Cap" business would not have resulted in the expensive liability issues. Quote from movie Caddy Shack: Rodney, browsing pro shop,"Nice hat, you get a free bowl of soup with that? Sees Ted Knight glowering with identical hat..."Looks good on you though!".

No that's the first thing we looked at , moving the bed can't work due to shape of room and location of ensuite

What frequencies and sound levels have been measured in the bedroom? Without some actual data rather than hearsay it's hard to determine what is needed.

The homeowner won't care about "What frequencies and sound levels have been measured in the bedroom." The only thing he cares about is his conclusion (to whatever degree that it might be incorrect) that it is something called 'EMI', and the subsequent solution (or visible effort to effect that solution) to his perceived problem.

People are funny creatures, and the homeowner has it in his head that this is the problem. Headsup, rather than simply provide a placebo (which may actually work to placate the owner), is investigating possible solutions that might actually help whatever the real problem might be (if it truly exists at all).

The symptoms you describe could be caused by many different things, including new pillow(changing neck angle), humidity and/or temperature, change in sheet or blanket/comforter material, different noise type or level in new location, emotional anxiety, new mattress, air quality(chemical residue).....this could take some time to work itself out, as you could just be chasing your tail, so to speak, by making changes and adding to/or perpetuating, the problem....my best guess is that it is, as others have said, an electrical hum of some sort....but as an aside, I would test the theory by having the subject try sleeping with ear plugs...then going from there...In any case people can get used to most anything, other than biological/chemical contaminate...

Have there been prior complaints about it from other tenants?

How much money you going to throw at this to appease a tenant? There could be numerous causes for this problem. One of which could be medical. Have they seen a doctor? Others could be the change in environment. How long they been there? Outside noises they are not accustom to. An allergy to some new furnishing that they purchased during the move in. Could be job related.

Common sense to me is if I thought it was caused by an electrical panel close to the head of the bed. Would be to sleep with my head at the foot of the bed to see if the problem went away or receeded. Only after confirming the problem is the electrical panel would I address it with the landlord.

It could also be a means to another agenda. Like a reduce rent.

I think you're making a couple assumptions, here, viz:

• That the complainant is a tenant (rather than a homeowner)
• That the OP is responsible for (and financially liable for) the amelioration of the situation.

It remains to be seen whether either is true.

Oz...do you have aluminium backed insulation in the wall cavity? It may already be EMI shielded. I'm assuming brick veneer....

If one walks for about 45 minutes in the evening at fixed times, nothing will bother his sleep.

Gajanan Phadte

A little test is in order:

If your subject is not DVOM savvy,this will be a good test.

Put your dvom on the 2meg or higher scale.

Hold the points of the leads in your fingers,and watch as the reading changes as you vary the pressure on the lead points.

Walk around the room,varying the finger pressure as you go,and showing the reading to your subject.

They should be higher near the suspected wall,lower as you walk away.

After installing fine mesh metal screen wire (Copper is available,but EXPENSIVE;aluminum is just as good for the purpose;Both metals are diamagnetic) in the wall,and grounding it to the power ground,repeat the preceeding steps with the meter set to the lowest ohm setting with the leads shorted.

Show the readings to the subject.

This will cure both possible causes of the problem,both real and imaginary.

Good luck!

Cheapest would be grounded aluminium sarking.

The department of spooks in Oz specifies grounded galvanised chook wire to shield sensitive communications structures. Works in both directions.

As I mentioned in a previous reply,screen wire is available in aluminum or copper metal.

It is much cheaper bought as a screen than as a fabric,and I think it will perform just as well.

The copper screen wire is typically used to prevent entry of pigeons,mice,rats,etc. in industrial applications.

The copper screen is available for about $2 per square foot.

For rf shielding, the aluminum should work just as well,if grounded properly.

If you want to take it to a higher level, charge the screen with HVDC.

I won't comment of the reality of the owner's claim, only on shielding. At line frequency mu metal is the best shielding, several thin, isolated layers. Probably too expensive in the size you need. Next best is steel foil. Maybe 3 layers isolated by heavy paper. The affect may be psychological, but that's OK too.

Careful you don't get marked off-topic for mentioning Mu metal. OP done made me mad. <unsubscribe>

With this type of situation/complaint the first thing to do is to get somebody to come and measure what frequency is the perceived culprit and the strength of the EMS (Smog) at 50/60 Hz and if this is in actual fact the problem. The chance are that a nearby cell tower or some other higher frequency may be the problem. The EMS from a 3 phase cable where the phases are separated 120 Degrees, Part of the cycle radiation is smothered by the phases be partly of opposite polarity. I will also assume that the cable is an armored double insulated cable. Take a loop current measurement on the cable around the armored part with all 3 phases loaded to get a current reading that will give you an idea of the EMS it can radiate.

If you have answers to what you want to protect the person from do the research on that.

If the cable is the problem, have it electrically isolated, disconnect it and put it inside a metal conduit of the specified size for maximum distance you can and that will give you the shielding you need for 415 V at 17 Amp. The Main switchboard in South Africa for Higher than 220 V must be steel, if yours is plastic you need to cover that but I doubt that it is plastic.

A good decorative laminate inside the bedroom, where your disturbance of EMI is there would do the job, as the laminate acts as a good insulator. Try to use a thicker one, than used for laminating wood.

Anything that the owner believes would work should be effective.

Anything less than λ /4 in size, the 50 hz field & wave will go right around. in this case you need a wall 930 miles high and wide, but more practically a grounded faraday cage surrounding all walls, floor and ceiling of the room. aluminum foil will work just fine.

If a person is locked in a room even he himself locks from inside, and if he cannot sit relaxed in this condition for 20 to 30 minutes , then the problem is not in the room.

Gajanan Phadte

Can said person have a cigarette?

Just doing nothing.

So you mean a chilled dead person?

Could the subject have mild tinnitis? So he only hears the ringing while in a quiet room.

Otherwise, my solution is to hang your fine wire mesh and then hang a rug/tapestry over it. Using the rug eliminates the construction involved with drywall , is easy to remove if it doesn't work, blocks sound, hides the mesh, and may even look nice.

Great idea.

will advise early next week on the outcome of before and after testing

How old is the complainer?

Does he sleep alone? If yes read all the other answers.

The tin foil hat only works when it is a pin hat.

For acoustic humming I tried a silent headphone (as Bose makes some) but because I have presidential ears they keep hurting even with no headphone on. I now consider even a cast. (they might be broken)

When I was young, good sex helped for everything, but now I get even headache thinking about it.

If no, perhaps he needs to try somewhere else or with someone else and do a comparative test between the two situations and come back with details for further analysis by the forum experts.

Here's an idea. I would first try one of these products to see if it helps. http://www.soundproofcow.com/Sound-Absorption-Materials/

If it does, then your next concern will be to make it look nice. I don't think the owner will want to see panel strung from the ceiling!

Really? You marked me off-topic when all I did was talk about the topic.

<Unsubscribes>

If you're referring to your post #53, it was an own goal. You replied to my post #31 which I had intentionally left marked as OT (and hence had 5 OT's). Replying to an OT post automatically checks your "Yes, this comment is very likely to be considered to be 'off-topic'." box - so (unless you manually un-check it) you will get 5 OT's.

Just because you're paranoid, it doesn't mean they're not out to get you! .

P.S. Did you really unsubscribe? PM me if you like.

No, I didn't really unsub. But I learned several things from this thread and will hopefully have the opportunity to use them in the near future.

okay i have an update

The interior wall cladding was removed.

there was 2.7 metres of excess 3C+E 3 phase cable coiled up in the wall cavity , this was trimmed back and reconnected , a couple of single phase cables were also shortened by 1 - 2 metres each and reconnected , but fastened with saddles at a distance away from the 3 phase.

The 3 phase cable was coiled "messily" in such a way that it was touching both galvanised steel wall frame studs behind the switchboard.

We may cover the main supply cable with a galvanised steel conduit tomorrow , didnt decide on that yet.

Two steel studs were also removed and replaced with timber

We are optimistic that the excess coiled cable touching the steel studs is probably most of the problem.

We may yet put shielding up when the cladding is replaced but that will be 2 -3 weeks wait from overseas

thankyou for the many intelligent replies.

two things i learnt from this;

Electricians are not always as stingy as they could be when it comes to recycling copper.
When you have a build up of gas after lunch , check the homeowner did in fact go outside when you heard the front door close before you let something loose in her bedroom .

It has been a very long day ...