@restorer-john what do you attribute this hummmm to? I think if the power line is active as in in-service then they must maintain ground reference albeit at a lower power rating.
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
120 hz hum-- not from my audio gear but from my house-- what to do about it?
- Thread starter Andolink
- Start date
The story of the 3 large size audio transformers used in the 1960s MCIntosh power amplifiers (e.g. MC275) were potted with a compound that contained nasty (carcinogen?) chemicals used to prevent any 60Hz hum caused by the close-coupled winding that may vibrate... One of the reason that was cited (as I recall) for their discontinuation. In the early 1980s, McIntosh broke the news that a pallet of these transformers where found in some warehouse and that they would make a limited quantity of SeriesII MC275s.
While working for on some military ship-borne massive communication suite, the 400Hz power required for energizing parts of the RF power systems in a shielded chamber, the needed MAINS' power-factor correction coils that were mechanically/galvanically isolated from the chamber but would sing so loud (~102dB/A), live qualification testing could only be achieved after-hours and the technicians (w/headphones) were only allowed to stay in the SCIF labs for no more than 4 hours per day.
That 400Hz
hum continued for three months straight, but we were lucky no one had gone postal on us!
Fascinating stuff for sure. Is this something you worked on with the 400 Hz mains?The story of the 3 large size audio transformers used in the 1960s MCIntosh power amplifiers (e.g. MC275) were potted with a compound that contained nasty (carcinogen?) chemicals used to prevent any 60Hz hum caused by the close-coupled winding that may vibrate... One of the reason that was cited (as I recall) for their discontinuation. In the early 1980s, McIntosh broke the news that a pallet of these transformers where found in some warehouse and that they would make a limited quantity of SeriesII MC275s.
While working for on some military ship-borne massive communication suite, the 400Hz power required for energizing parts of the RF power systems in a shielded chamber, the needed MAINS' power-factor correction coils that were mechanically/galvanically isolated from the chamber but would sing so loud (~102dB/A), live qualification testing could only be achieved after-hours and the technicians (w/headphones) were only allowed to stay in the SCIF labs for no more than 4 hours per day.
That 400Hz
So so-called ‘hum’ that plagues people world wide seems to be around 40-50 hz. 120 hz has to be related to the 60 hz grid somehow. But why 120 and not 60 is even more curious.
What do you mean by 'all around the neighborhood'?
Who was the builder who built the development, eg., Lennar? Do you have a new home warranty?
It's possible the power lines were never installed properly...you might (a big might) be able to find out if the power utility or whoever inspects them signed off on the installation.
Last edited:
? Wouldn't "improperly installed powerlines" cause 'noise' (arc/spark) rather than "hum"?
I have never heard of (or seen) above-ground powerlines which showed to be 'vibrating' at frequency-of-operation or its harmonics... but I don't get out much anymore.
Trying to find the location of the transformer(s) serving the community's powerlines may lead to a missing clue. ymmv
I read once DXers get a post hole digger, a bag of ferro-cement and 4 ft piece of re-bar and dig a deep hole, mix and fill the hole with cement and rebar. After it dries the ground wire from a dedicated circuit(s) is run to the re-bar for dead quiet operation.
Disclaimer: I'm a ME
Disclaimer: I'm a ME
Old phase forward dimmer switches are notorious for sending hum everywhere.
Maybe walk around the neighborhood in a grid pattern recording the volume of the hum to help locate the source. Correlate to location with GPS.
JSmith
Master Contributor
Why do power lines buzz?
When near high tension power lines, particularly after a good rain, the lines themselves emit a buzzing noise. A similar noise can be heard coming out of the electric meters attached to my apartmen...
physics.stackexchange.com
Why does electricity hum -- and why is it a B flat in the US, and a G in Europe?
Who knew sound and current can intertwine so much?
www.zmescience.com
JSmith
sam_adams
Major Contributor
- Joined
- Dec 24, 2019
- Messages
- 1,004
- Likes
- 2,454
Why do power lines buzz?
When near high tension power lines, particularly after a good rain, the lines themselves emit a buzzing noise. A similar noise can be heard coming out of the electric meters attached to my apartmen...
Why does electricity hum -- and why is it a B flat in the US, and a G in Europe?
Who knew sound and current can intertwine so much?
JSmith
The first link is nonsense. The 'buzzing' that one hears near HT lines—10, 12, 15 KV or higher—is caused by arc-over on the insulators due to the moisture content in either the air—think heavy fog, drizzle, light rain—or actual liquid water or dirt/debris on the lines and poles. It's more of a crackling/sparking/arcing noise than a hum—and in dry weather—usually indicates that your local electrical utility hasn't cleaned the insulators in a long time. The local utility in my area has specialized trucks that have a high pressure water jet system that blasts the accumulated dirt and debris from the HT line insulators to prevent that specific situation from occurring since it causes an actual loss in delivered capacity.
The second link involves ground loops. The author obviously has never heard an angry three-phase motor that was wired wrong or a buck/boost transformer wired out-of-phase. Hum is the 50/60 Hz fundamental. Buzz is the odd order higher harmonics. Bill Whitlock has explained that, ad nauseam, for decades.
No but things that use transformers have similar issues. Shut all breakers off and then turn them on one by one only to see if it is a isolated issue.
Thank you for the articles but both are quite hard to swallow (as explanatory), yet some included factoids are valid.
I think once the EXACT definition of hum (60Hz/120Hz?) is made we can further discuss the source but once hum becomes universal word covering every type of noise (thru out the RF spectrum); then, we got ourselves a whole different argument that should be left for another thread.
This "hum" we are attempting to discuss from different perspectives has been referenced (in your links) as either the magnetic component and/or the electrical field of "power" we can call the 50-60Hz (+few harmonics) MAINS.
Granted the 'hum' due to magneto-striction effects of close-coupled wiring (as in a live coil/xfrmr) is a valid source; yet, to blame straight-line MAINS wiring overhead for the source of the this particular type of 'hum' is a big reach. imo
Your links also 'speak' of speaker effects; as if a straight-wire that is not exactly tuned to the wavelength/partial of the source frequency (MAINS=50Hz or 60Hz) that cannot be expected to sing like a tuned port.
That dude @sam_adams [who always seems to have migraine headache
] makes sense to me more than anything those two articles lay out.
Last edited:
Everything off where is it coming from, the air?
No, @Timcognito, it is not what a GroundFaultInterrupter does either! Literal or figurative.
If not by air, and not by ground... then, it must similar to what @thegeton suggested elsewhere:
"Catfish, anyone?"
I've often heard hum/buzz from HV power lines. Actually from the pylons rather than the lines.
It would not be a big surprise if the magnetic field generated by up to 4000A moved some stuff at mains frequency.
OP
Andolink
Active Member
- Thread Starter
- #80
Exactly! That's the thing that's driving me batty. What's the source of this hum?? My wife hears it too so it's not my tinnitis or one sided hearing loss. In fact, my hearing problems exacerbate my already acute sensitivity to background noises of all sorts, hums, autos, sirens, airplanes, etc., etc. And, as I said, when I walk down to the end of my street or anywhere else in my neighbohood, if the ambient noises are relatively low, there's the hum.
