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Sound from Electrical devices

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ElectroEnthusiast

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When i was walking on a road, i heard some noise(rattling sound) from a lagging high-tension transmission line. I did read about some related topics from google. My question is why does it produce noise? How does it happen? Is'nt it loss in Power?

Another question, why do transformers produce a similar humming noise?
What makes this sound happen?
 

darkseid

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The humming sound from transformers is due to magnetostriction and the Residential Power supply operates at 50/60 Hz which is well within the audible range. The rattling sound from transmission line is due to the formation of corona/streamers due to the extremely high voltage. There is quite a lot of physics involved.

regards
Darkseid
 

andre_teprom

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There are some reasons to some kind of sounds :

At domestic use ones (power supply / UPS / etc), means that some external lamines are not well glued by varnish.
So, the Lorentz force applyes a movement syncronized to magnetic flux ( i.e 60Hz ).
At high-voltage public distribution ones, may be origined for bad insulations.

In both cases wasted energy have no much significance.

+++
 

thannara123

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In energized transmission lines, electric fields around a conductor can become concentrated enough to create an electric discharge. This type of discharge is called a corona and ionizes the air around the conductor. Conductor voltage, shape and diameter as well as scratches, dust and water can affect the conductor's electrical performance and the creation of coronas. Forming on the transmission line, a corona is what occurs when there is energy loss along the line.

When a corona forms, there can be audible noise coming from the transmission line. A crackling or humming sound is generated by small electrical discharges, often caused by water drops that collect on the conductor when it rains or there is sufficient moisture in the air. The EPA has set noise guidelines of 55 dBA for transmission lines, as this is within the range that has been measured during rain.
 

liteon

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A very high voltage very heavy transmission line passed within 2 kilometers of my old village house.When i was a young boy my father used to drop me to school he had to pass under that line daily.The Radio of his car always stopped within 10 feet away from the line.Recently we found that All kind of radio transmission either mobile phone radio Television won't work when close enough to that line and we always heard buzzing sound.
We also heard from truck drivers that during the rain and for some time after the rain that men sitting over the truck's roof always felt some feeling like a rash on the body as if there were insects crawling on their bodies,yet the hight of that electric line is almost 25 feet from the roof of the vehicle.The reason behind this is the moisture in the air carries small amounts of electric charge come in contact with the body and causes tingling.
 

ElectroEnthusiast

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Yes, i did find that the sound was due to moisture. But, i guess the loss in power would be negligible.

---------- Post added at 06:09 ---------- Previous post was at 06:04 ----------

The humming sound from transformers is due to magnetostriction and the Residential Power supply operates at 50/60 Hz which is well within the audible range. The rattling sound from transmission line is due to the formation of corona/streamers due to the extremely high voltage. There is quite a lot of physics involved.

But ' How can magnetostriction cause a sound? '
 

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