You have an arc-over somewhere in your power supply system. Electric arcs produce a broad band signal with precisely that noise pattern.
Cracked or dirty insulators on the power poles, transformer with an internal primary circuit fault, loose connections between the transformer and meter, or compromised underground feeder cables that are leaking current between the conductors will probably be the source of this EMI.
Heaven forbid that the source is anywhere in the house, that's a dangerous situation.
Determining where it comes from
Given the noise that can be heard in the video, this should be transmitting a pretty nasty interference on AM radio frequencies to the point you should have no problem using an AM radio as a source detector.
First steps are to make sure this isn't something in the house that is suffering from a loose connection, ground leakage or arc fault. Turn your radio on and with it somewhere mid band between stations, see if you can hear the noise. Now go through the breaker panel or fuse panel and cut power to each circuit till you have cut all power to the house.
If the noise goes completely away from powering off a circuit, then start looking for appliances, switches, lighting fixtures powered by that circuit that that have failures. At this point, if wiring starts being the possible culprit, you're getting into electrician territory, so get a qualified electrician if you're exceeding your technical expertise or what you're allowed to do under your local laws.
Using this method, I had found that the people who wired my house up had used a crimp ground ring to complete a power circuit in the bathroom which explained the radio noise and the dim lighting that would flicker every so often. Removing the electrician's tape off the odd looking connection revealed that the crimp ring (improper use, only supposed to be used in the ground circuit) had worked loose and the copper wire was being slowly eroded from the arcing in the loose connection.
If the power down only slowly diminishes the noise till the last circuit is cut off, then you need to make sure the power entrance and cabling to the breaker panel/fuse panel are intact to clear your residence (qualified electrician time, you do not want to be messing with this).
Once you have cleared your residential wiring, then you need to get the power company involved in hunting down where the noise is emanating from. It's in their best interest to fix it if its a bad splice, cracked insulator or transformer getting ready to blow.
Yes this is indicating a problem. It's hard to tell what the issue might be, but electricity is silent when its working right.
BEFORE INVESTIGATING - turn off the breaker.
Things I would check AFTER turning off the breaker:
- take off the outlet cover and look for
- burn marks
- loose wires
- cracked or worn insulation
- cracked or worn parts on the outlet
- signs of rodents
- take off the switch cover and look for the same things as the socket
The easy try-it-and-see repair is to replace the switch and outlet, this should cost maybe $10 and 30 minutes of work.
Do you know if you have aluminum or copper wiring in your home?
Is there a fan in this bathroom? Are you sure the noise was coming from the outlet and not a breeze blowing past the fan?
Best Answer
Transformers
The sound you're hearing, is likely caused by transformers. It's a common problem, and a normal phenomenon.
Most wall warts consist of a transformer to reduce the voltage, and a rectifier to convert alternating current to direct current. So anywhere there's an AC adapter, there's likely a transformer.
This document from Federal Pacific (PDF), explains the phenomenon that causes transformer hum well.
Loose Connections
If you're hearing the buzzing from receptacles (sockets), it could be caused by a loose connection. If a connection in the receptacle is loose, there could be arcing taking place. Arcing could definitely cause an audible sound. However, arcing would also generate heat, which could lead to a fire. It's best to contact a local Electrician to come have a look. If you're familiar and comfortable with electrical work, you could check the connections and/or try replacing the receptacle (socket).