resonance of electrical cables into house turns our bedroom into a guitar

[speedracing944]

I am hoping to tap into some of the knowledgeable folks here. The problem we have had for the 8 years we have been in our home is the main power cables which run from the power pole to the corner of our house transmits a unbearable vibration into our bedroom. The vibration can be heard on the outside power lines as well. It creates a loud, low frequency hum which reverberates through the entire room. The vibration is more noticeable during the winter months when it is cold outside. It is to the point to where we can no longer sleep in our bedroom at night. In the past, the electric company placed dampers on the power cables which resemble giant springs. This appeared to help a little but it could have been more of a placebo affect. I once had them lessen the tension on the power cables but all this did was vary the pitch of the vibration. The cable was hanging too far down to be considered safe and was tightened up again.

I am thinking there is a natural resonance frequency of the system, sort of like a guitar spring. I am not sure what is causing the system to resonate though. The only correlation I have been able to come up with is temperature.

How do I go about eliminating this problem? I am at my wits end and my wife is talking about just selling the house.

1880's farm house
1.5 stories
Power cable is attached to the corner of the house at the eave

Speedy

[Heel n Toe]

Earplugs and a white noise machine.

[speedracing944]

Karman-Vortex-Street excitation?

[aigel]

Stop the power at the corner of the lot on a pole, then run in the ground into the house.

The vibration could be like a string on a guitar but may more likely be in the direction of the line itself. It would not hurt to ask them to hang some of those wind deflectors off the line to see if you can break up the resonance frequency to where it will be off from the exciting frequency enough to stop it ...

George

[look 171]

Originally Posted by aigel

Stop the power at the corner of the lot on a pole, then run in the ground into the house.

The vibration could be like a string on a guitar but may more likely be in the direction of the line itself. It would not hurt to ask them to hang some of those wind deflectors off the line to see if you can break up the resonance frequency to where it will be off from the exciting frequency enough to stop it ...

George

That's a lot of money. Cities like So Pas are making residents to do when they have to upgrade their panels. Crazy money.

[GWN7]

If you like the house and the only problem is the vibration then go underground as mentioned above. The cost/stress to sell/find a new place and the moving costs would be far more than going underground. Talk to your Electrical utility about it, they may share some of the costs.

My utility charged me $1750 to run a line 75' to a pole (I supplied) and mount the transformer (they supplied). I went underground from my pole to the farm house. The wire for the underground run was about $500

[HardDrive]

Originally Posted by look 171

That's a lot of money. Cities like So Pas are making residents to do when they have to upgrade their panels. Crazy money.

In the process of spending $30k for a new underground electric feed into my house. 2 driveways replaced, rockeries, landscaping......brutal.

In regards to the problem at hand, can something be done to the mount point where the line attaches to the house? Is there a transformer on the pole that feeds the line to your house?

[red-beard]

Originally Posted by speedracing944

I am hoping to tap into some of the knowledgeable folks here. The problem we have had for the 8 years we have been in our home is the main power cables which run from the power pole to the corner of our house transmits a unbearable vibration into our bedroom. The vibration can be heard on the outside power lines as well. It creates a loud, low frequency hum which reverberates through the entire room. The vibration is more noticeable during the winter months when it is cold outside. It is to the point to where we can no longer sleep in our bedroom at night. In the past, the electric company placed dampers on the power cables which resemble giant springs. This appeared to help a little but it could have been more of a placebo affect. I once had them lessen the tension on the power cables but all this did was vary the pitch of the vibration. The cable was hanging too far down to be considered safe and was tightened up again.

I am thinking there is a natural resonance frequency of the system, sort of like a guitar spring. I am not sure what is causing the system to resonate though. The only correlation I have been able to come up with is temperature.

How do I go about eliminating this problem? I am at my wits end and my wife is talking about just selling the house.

1880's farm house
1.5 stories
Power cable is attached to the corner of the house at the eave

Speedy

A couple of things:

Describe the cable entrance into the house.
What is the material of the cable: Aluminum or Copper?

Hum usually is generated from the magnetic fields acting on something external. In a transformer, the steel body is excited by the alternating magnetic fields, making the classic 60 Hz hum. Is there something ferrous nearby that is being excited by the cable? Does the cable enter into the house in a "pipe"?

If it is entering the house in a "conduit" made of iron pipe, you might want to consider changing it to actual aluminum conduit, or preferably a plastic conduit. Maybe it is near some sort of drain gutter, steel support, etc. In those cases, you might consider relocating the electrical feed away from the ferrous material. Or finding and removing the ferrous material.

[IROC]

I know nothing about this (what a way to start a post ), but it seems like the natural vibration of the electric cables is exciting your room at some natural frequency. It seems that ways to avoid this is to change the input frequency (can't do that) or change the stiffness/mass of the room to move that natural frequency node away from 60Hz.

In the engineering world, this is actually a common problem. I've worked on projects where we had to consider the frequencies of the shuttle engines and also C-130 engines and design the structure's modal frequencies to avoid coupling. Of course, designing a structure out of aluminum and changing it's frequency is easier than a room in an old house.

[HardDrive]

Are you averse to installing a 4 ton concrete dampener in the attic?

[Pazuzu]

Toss a pair of shoes over the line. if it's an actual vibration, that'll change the frequency. If it's a resonant issue with the 60hz signal, it won't.

One way or the other, the gangs will stay out of your yard, since you marked your territory

[VINMAN]

Mine goes to eleven....

[jyl]

Is it a mechanical effect or an electrical effect.

If mechanical, it wouldn't seem that terminating the overhead cable at a pole at the boundary of your yard then going underground, should cost too much. Presumably the pole can be located to make the underground run easy.

Or, even cheaper, could you sink a pole 2 feet from the corner of the house, run the cable to there, then have the cable be very slack for that last 2 feet to the house? The pole can vibrate all it wants.

If electrical, then I dunno but the steps James outlined don't seem too hard.

[scottmandue]

Originally Posted by IROC

I know nothing about this (what a way to start a post ), but it seems like the natural vibration of the electric cables is exciting your room at some natural frequency. It seems that ways to avoid this is to change the input frequency (can't do that) or change the stiffness/mass of the room to move that natural frequency node away from 60Hz.

Thinking the same thing... or if it is electrical resonance... can you install an isolation transformer where the line enters the house?

[HelmetHead]

Just a thought....What about putting a pole half way down the line from the man power lines to where it ties into your house?

[porsche4life]

Originally Posted by jyl

Is it a mechanical effect or an electrical effect.

If mechanical, it wouldn't seem that terminating the overhead cable at a pole at the boundary of your yard then going underground, should cost too much. Presumably the pole can be located to make the underground run easy.

Or, even cheaper, could you sink a pole 2 feet from the corner of the house, run the cable to there, then have the cable be very slack for that last 2 feet to the house? The pole can vibrate all it wants.

If electrical, then I dunno but the steps James outlined don't seem too hard.

Originally Posted by HelmetHead

Just a thought....What about putting a pole half way down the line from the man power lines to where it ties into your house?

That was suggested.....

[M.D. Holloway]

hang a pair of Air Jordans from the wires, seems to work in the hood

[notfarnow]

Funny, I have a similar problem in my ~1870's farmhouse!

And we're not alone:
Odd noises at the house...