Ambient Electrical Noise?

[earlz]

Ok, So I heard this story that a farmer once lived near a power distribution center, and that the barn which housed animals was rather close to it. I heard that the light bulbs in the barn never went off completely because of the strong electrical currents in the air due to the power distribution center, so it was therefore basically just wasted electric floating in the air...
Is it possible that this really happened?

Ok, I have a guitar amp which has a CD-in which amplifies an input source completely "pure." no distortion or anything.. .well I've made some observations and I can't quite understand them...

I did all of these observations with an unshielded regular audio cable and my amp is grounded.
First off, I can't seem to find this answer, but does the tip of the audio plug represent positive or negative?

Ok.. now why exactly does white noise get produced from an unplugged cable, especially when poiinting the plug around certain strong electrical devices? I can understand if it is a thing like current is produced through the plug and cable and such. But whenever I "short" the audio plug(have it to where the two wires connnect) then there is no noise at all.

Ok, and another strange thing.. I seem to be able to "carry" noise. Like I have a black box power transformer thing for my external harddrive.. it is very noisy, when the plug is near it, it's the loudest thing in my room basically.
If I wrap copper wire arround this box and then drag the copper wire a few feet away and put the plug near this copper wire, I get the same noise(same pitch and such) but slightly quieter depending on how wrapped the box is in copper(the more wraps, the louder) and if I touch the tip of the plug to the copper it is very loud, though a different noise. The noise that touching the tip to metal gives is not a constant pitch.. it seems like a square wave, which leads me to believe it's made from the AC current around my room. If I just have a stray piece of copper wire around my room and touch the tip to it, I get the same sound, and it is equally loud. But when the tip is not touching such a wire, then their is very little noise(or very quiet).. why? But anyway when I have the copper around the blackbox, and I touch the copper wire with my hand(ungrounded) then there is no noise, and if I touch the tip of the plug to the wire and then touch it with my hand, It seems to get a little quieter, but also changes the noise to a different square wave.

Oh, and another strange observation. Attaching a piece of copper wire to the base of the plug makes it noiseless. and touching the tip to my hand makes a square wave, but different from the seemingly ambient one around all of my room.

Ok.. and I suppose I should say this one too cause I'm baffled by it. If I hold the base of the plug with my hand(ungrounded) and rub it against my rubber shoes, I hear noise only while it is rubbing against my shoes It seems to work this way all around my body no matter what the material rubbed against is(you can hear the texture as if you had a stick rubbing it). Is this static electricity being heard? Oh, and whenever I'm not touching the base, nothing is heard that way..

I'm just having this huge idea and to figure out if such an idea is feasible, I need to know the answer to these questions.. I have read wikipedias stuff on EMI and noise and all that.. but it seems to be irrelevant to this.

Edit:
Oh wait.. another interesting thing.. when I wrapped the copper wire around the black box, and strung it out a few feet.. the copper kinda spooled into the air cause the copper came off a spool.. well when I took the plug to hear stuff, I noticed that about a foot away from the cable, there was this small area in which I heard fairly strong ambient square noise, and the area was only like 1 cubic inch or so(or like 3 cm) and when taken out of this area ambient noise was fairly quiet again, like suddenly, it was either in the area or wasn't. I then noticed if I moved the copper wire with the plug, I could direct the area, which means this copper wire is sending out the noise in a certain direction and in a certain wavelength. I actually never tried moving the plug horrizontal to where the area was, so I'm not sure on that much. Also, this could have been inaccurate, so if this really makes no sense at all, then tell me and I'll try to test it more thoroughly as it could have been a coincidental hotspot or something in my room somehow.

Also, the blackbox transformer is not grounded.

[JohnnyTheDon]

Ok.. now why exactly does white noise get produced from an unplugged cable, especially when poiinting the plug around certain strong electrical devices? I can understand if it is a thing like current is produced through the plug and cable and such.

Most likely electromagnetic induction. Any moving magnetic field (like the one created by a wire with AC current or signal running through it) relative to a conductor induces a current. I once heard a story about a guy who messed with his power supply in his computer and ended up running 120V of outlet power through his case. It blew out his speakers

Ok, and another strange thing.. I seem to be able to "carry" noise. Like I have a black box power transformer thing for my external harddrive.. it is very noisy, when the plug is near it, it's the loudest thing in my room basically. If I wrap copper wire arround this box and then drag the copper wire a few feet away and put the plug near this copper wire, I get the same noise(same pitch and such) but slightly quieter depending on how wrapped the box is in copper(the more wraps, the louder) and if I touch the tip of the plug to the copper it is very loud, though a different noise.

You're now inducing current in the copper wire, which then induces current in the plug.

The noise that touching the tip to metal gives is not a constant pitch.. it seems like a square wave, which leads me to believe it's made from the AC current around my room.

IIRC AC is sinusoidal, not square wave.

But anyway when I have the copper around the blackbox, and I touch the copper wire with my hand(ungrounded) then there is no noise

You're hand is grounded enough to provide the small induced current an alternate path.

I hear noise only while it is rubbing against my shoes It seems to work this way all around my body no matter what the material rubbed against is(you can hear the texture as if you had a stick rubbing it).

That is probably static electricity. The plug is pulling electrons from your clothes.

I'm just having this huge idea and to figure out if such an idea is feasible, I need to know the answer to these questions.. I have read wikipedias stuff on EMI and noise and all that.. but it seems to be irrelevant to this.

It's not irrelevant at all, most of the stuff you described is EMI in some shape or form. Electromagnetism (IMHO) is one of the most interresting topics in physics and I recommend looking in to it some more, but I wouldn't make wikipedia my primary source.

[JackScott]

The tip of an audio cable (balanced or unbalanced) represents neither positive or negative. If you have a constant pitch of 1000Hz, you have a sine wave that fluctuates between -1 and 1, 1000 times a second. -1 is the negative voltage, 1 is the positive. The standard value for the -1 and 1 is a thing known as a dBU (decibels unity), IIRC. The sleeve of the cable plug is a ground, which represents the value 0.

[Firestryke31]

I have a pair of PoS speakers that are extremely sensitive to any EMI. Doorbell goes off? The spark in the relay causes my speakers to pop. Starting the stove? Every time the igniter goes off my speakers pop. My cell phone causes the most horrendous noise simply by being in the same room. The speakers are powered and don't have a ground prong on the outlet plug, so I'm sure the EMI could be at least reduced by replacing the speakers with a pair that are actually grounded.

Oh, did I mention I can get one of the local radio stations somewhat clearly if I unplug the audio line and turn the volume all the way down (but not off) and plug in a pair of headphones? 103.5 Bob F.M. really will play anything, from rap to the chicken dance (no, seriously, they've done it).

[xenos]

You can do a lot of nice stuff with these EM signals. I once made some experiments with a small amplifier I built myself, that just caught EM signals with a small antenna, amplified them, and made them audible with a speaker. Then I listened to the "EM sound" of some devices I found:

• Remote controls make a nice, beeping sound when a key is pressed - the current that flows through the infrared LEDs is strong enough to generate a weam EM field in its vicinity.
• Turning on the amplifier in a lecture hall full of students was a complete mess - some of them had mobile phones turned on, making some kind of knocking noise.
• Being close to an AM radio station was also an interesting experience...

You can also try to analyze the noise spectrum if you have an oscilloscope. If you just plug in a cable, you will most likely see a 50 (or 60, depending on where you live ) Hz sine wave, induced by the AC supply.

I once had a strange problem when I was in a physics lab and I tried to record the motion of a pendulum with a position sensor. There was a nice 1 Hz sine wave, which was the motion of the pendulum - but it was buried in 20 kHz noise, and I could not find any explanation for that. I switched off computers, monitors, light... nothing seemed to work. I even computed the frequency of the HERA particle accelerator unterneath the lab But, finally, I found the reason: The switching power supply for the pendulum was broken. Using a different power supply killed the noise.

[frank]

I've got a question now then. Why do all the power supplies make a high pitched squeal? I've got a crappy lexmark printer that always does it if the power is plugged in, but my laptop only makes it when its asleep and then the sound goes on and off with the led (you know the little one that pulses to let you know the computer is asleep.)

[Solar]

[barn lightbulbs]

Is it possible that this really happened?

Absolutely.

If you live close to a strong radio station, you can light a bulb simply by attaching it to a length of (unshielded) cable. (This is illegal, at least here, but possible.) Radio signals are electromagnetic waves, and when you receive them via an antenna what you're doing is transforming those waves into electricity, which your radio then amplifies and makes audible through the speakers.

All the things you are describing are applications of the same basic principle. Some of what you're telling about indicates badly shielded / grounded equipment.

And since electromagnetic waves are used e.g. in medical applications, to effect biological effects in your body, it should be clear that less electromagnetic waves around you would be better. (That's why computer cases are metal, not plastic...)

[earlz]

[barn lightbulbs]

Is it possible that this really happened?

Absolutely.

If you live close to a strong radio station, you can light a bulb simply by attaching it to a length of (unshielded) cable. (This is illegal, at least here, but possible.) Radio signals are electromagnetic waves, and when you receive them via an antenna what you're doing is transforming those waves into electricity, which your radio then amplifies and makes audible through the speakers.

All the things you are describing are applications of the same basic principle. Some of what you're telling about indicates badly shielded / grounded equipment.

And since electromagnetic waves are used e.g. in medical applications, to effect biological effects in your body, it should be clear that less electromagnetic waves around you would be better. (That's why computer cases are metal, not plastic...)

wait it's illegal to have a radio station that strong or to attach a piece of copper to a light bulb? lol

and there are quite a few plastic computer cases out there...

and for the.. lighting the lightbulb trick.. a bigger antennae attached to the light bulb would make the bulb brighter right, or would it somehow get wasted with the bigger length of wire? and if you had a big flat sheet of aluminum foil, and then attached a piece of wire to it and then to the light bulb, would that work better or worse?

Ok, and what about EMI from things like the sun? are those within audible range? and how strong are they?

[earlz]

Wow this is amazing.. I have this spool of copper wire and attached my audio speaker wires(playing music) to the copper and then put the audio plug of my amp inside the coil of wire, and I can hear the audio just perfect.. Maybe a little quieter.. but still amazing! and the wires are not touching.. this is amazing to me

[bewing]

Your copper shield around the transformer would work a lot better if it were connected at one end to something grounded -- like the center screw in the outlet. Don't connect to ground in 2 places -- this creates something called a "ground loop".

and there are quite a few plastic computer cases out there...

The insides of the plastic cases all have metal shielding if you look, and the metal shielding is connected to electrical ground through the power supply.

Ok, and what about EMI from things like the sun? are those within audible range? and how strong are they?

A) A lot of the white noise you hear from your unshielded cable is from the sun.
B) The fundamental EMI wavelengths that you hear from a celestial object are directly related to the size of that object. That is one reason that radio telescopes can tell you something interesting -- because the wavelengths that you receive are indications of the size of object you are "listening" to.
C) There is a formula called the "antenna formula" in physics. It says that if your antenna is smaller than 1/4 of the wavelength that you are trying to receive, then you will not receive much of it at all.
D) The sun is 93 million miles away, and the strength of a signal drops as 1/r-squared.
E) The radio emissions from the sun are VERY powerful, and can knock out an entire country's electrical grid, even at 93 million miles away.

and if you had a big flat sheet of aluminum foil, and then attached a piece of wire to it and then to the light bulb, would that work better or worse?

There is an entire sub-discipline of engineering, on antenna design. Study up for 8 years, do a few thousand computer simulations, and you may find the answer. In general, what you want is a loop (or as you have found -- multiple loops in a coil).

And since electromagnetic waves are used e.g. in medical applications, to effect biological effects in your body, it should be clear that less electromagnetic waves around you would be better.

This is paranoia. Yes, EXTREMELY strong EM fields can achieve medical effects. Weak fields have never been shown to have anything except slightly positive medical effects. The natural environment of our planet that all land species have evolved in for the last 400 million years includes some fairly powerful EM fields -- especially around thunderstorms.

Why do all the power supplies make a high pitched squeal?

Power supplies contain transformers -- which are two electromagnetic coils which attract and repel each other. This creates vibrations. The wires in the coils are supposed to be firmly held in place with epoxy resin -- however, a cheap transformer will vibrate a lot more than a well-made one. This is also why televisions and CRTs whistle. They have a flyback transformer inside that runs at a high frequency. Modern switching power supplies may vibrate at a significantly higher frequency than you can hear, but they still vibrate. A good power supply design will include some sound dampening.

did I mention I can get one of the local radio stations somewhat clearly ...?

I've got two cheap desktop stereos that receive cell phone and CB radio conversations -- REALLY LOUD (much louder than my music! ).

And all this is actually related to modern computers in one important way. SATA cables use small high-frequency signals to transmit a bitstream. And the cables are specced as being UNSHIELDED. So, imagine the difficulty of trying to pick a tiny bitstream out of the mess of white noise you hear from an unshielded/ungrounded cable.

[earlz]

wow this is all extremely interesting..

for the grounding stuff.. that doesn't make sense.. If I touch the wire, it will be quieter.. but then again I did touch it downstream of the receiver..

oh, and offtopic question.. are there any simple electrical devices that can "switch" the current direction? like if the current changes direction between a wire and a second wire, it could change it so the direction of the current would be the same as before to a third and fourth wire... oh and voltage stabilizers? is thre any simple devices that do not require external power to regulate a circuit to a certain voltage(even if amps or whatever had to go down or up to maintain this voltage)

sorry I don't know much electrical jargon lol

[Solar]

That's the point where I would suggest taking some kind of course in electronics. It will teach you the jargon, the devices, and the safety measures to be taken if toying with AC/DC.

Not the band, of course.

Re "paranoia": our natural environment doesn't involve thunderstorms on a 24/7 basis. I didn't suggest wrapping everything in tinfoil, either.

But I'd think twice if I'd put my multi-GHz gaming machine in an acryl display case, for example. 2.45 GHz is the wavelength your microwave oven uses for heating your food. Yes, that's orders of magnitude more powerful in wattage, but you are sitting amidst all those appliances for a sizeable portion of your waking hours, and if having your stuff grounded, shielded etc. doesn't improve anything, it doesn't hurt either.

That's why I had CAT.6 installed in every room when we refurbished our house, so I could do without WLAN repeaters. Faster, too...

[xenos]

There are even more impressive effects in the strong EM field of a Tesla transformer. For example, it is strong enough to supply a fluorescent lamp, without any wires attached. I once did a similar experiment in a physics lab, holding a fluorescent tube close to some setup that generated a standing EM wave pattern. It was really amazing to see the light move around inside the tube as I moved it through the wave pattern. I have some pictures, but unfortunately one can't see the light.

[bewing]

are there any simple electrical devices that can "switch" the current direction?

This is called a diode. The circuit you are asking about is called a rectifier.

oh and voltage stabilizers?

One form of this is called a clamp diode.

[earlz]

are there any simple electrical devices that can "switch" the current direction?

This is called a diode. The circuit you are asking about is called a rectifier.

oh and voltage stabilizers?

One form of this is called a clamp diode.

The way I understand diodes though is they keep current from going one way, they don't necessarily reverse it though.. or could that be done with two diodes? hmm I think I will take an electronics course soon when I'm in college.. (this coming fall) cause I would really like to know this kinda stuff.. heck I've considered doing a double major in programming and like hardware engineering or whatever the name is. I don't want to be the person putting receptacles in walls, but building microchips would be pretty fun..