What is this noise??? Any help ASAP would be much appreciated.

[gemini86]

My friend owns a studio in town and has had this noise show up on unbalanced gear, amps, etc. for some time now. Now it's gotten stronger and more frequent, and is bleeding into his balanced gear and everything in between. Any clue as to what it is and what to do about it???

https://soundcloud.com/thaddeus-moore/what-is-this-noise?utm_source=soundcloud&utm_campaign=share&utm_medium=facebook

 

[Brian Roth]

Years ago, I dealt with something somewhat similar at a local pro studio.  It even began to "bleed" into various mix buses on their MCI JH-636 desk.  In that case, the noise (more of a steady  "rasp") would start off below the noise floor of the desk, ramp up louder and louder for maybe 30 seconds, then abruptly stop...and then repeat the cycle.

I made an educated guess it was SOMETHING connected SOMEWHERE on the AC mains.  I went to my truck, and with engine off, tuned the truck radio to the low end of the AM band (like around 550 or 600 kHz) where there were no local stations.

Sure enough, I heard the same racket/pattern on the radio!  I walked around the building and finally spotted a security light (probably a mercury vapor or similar) on the rear of the building that was struggling to "start"...in broad daylight!

The photocell was obviously not working correctly, and the bulb and or/ballast was also not working, since the bulb would never fully illuminate.  The bulb would struggle and flicker, getting slightly brighter, then go dark, only to repeat the cycle.

So, try the AM radio trick and hunt around in the area for something hanging off the AC mains that isn't up to snuff.

Bri

 

[gemini86]

Thanks, Brian. Last time I was there, I managed to get the general direction of the noise coming from the back of the building (pointed a cranked electric guitar toward it, got louder) so maybe that's the ticket. There's likely a few larger street lamps back that direction.

 

[bruce0]

The numbers of pulses is different, sort of strange 6 - 7 - 8 pulses.

Sounds sort of like the zing you can hear in the rigging of aluminum mast boats from radar.. but that doesn't come in pulses.

Near the water?  Near the airport?

I like Brian's idea though, some kind of start process for a lighting system or motor system.

 

[gemini86]

Not near water, and a few miles from an airport. It's there always. My first thought was a broadcast tower of some sort, but since the frequency of the pulse groups has gone up, I'm thinking it probably is a street lamp that's been slowly failing, and now it's short cycling.

I'm going over there sometime this week, so I'll investigate, try out the AM radio trick and see what's what.

 

[bruce0]

Cheap transformer or coil unshielded connected to an oscilloscope makes a workable gauss meter.. if it is magnetic.

If it is higher frequency.. then I don't know... maybe an am radio.

 

[gemini86]

Well, went over there tonight. Had another guy with a nicer looking portable DSO, but could hardly pick it up from a guitar pickup. We ran it through a dual recto and crank it up, looked at it on the scope. Still not able to determine where it's coming from, or what type of noise it is... or even what to do about it if it's outside. It sucks really, he'll either have to move or close down if the problem can't be resolved.

 

[pucho812]

what are you using for light dimmers?  I've been in studios with cheap dimmers that intduce all kinds of electrical garbage into the audio.

The noise reminds me of a jackobs ladder you know where it has the two poles  and electricity runs between them going up?

 

[horvitz]

Is there any time of day correlation?  Might give you an idea if it's a human activity or not.  Like a news van or something.

 

[bruce0]

Is it constant, or just comes and goes?  I realize it is pulses of noise but does the pulse change?  is it clean at some times of day?

How about power quality.  It is well above 50 or 60 HZ, so put an oscope on the line and look for spikes above that frequency maybe?  There are (expensive) power filters of course. 

Is there any way to reproduce the noise on a small bit of equipment, and then run that off an inverter or generator (totally off grid)?  Or maybe you have some DC equipment that has the problem that you can run off a battery or clean psu?

It seems like you need to eliminate possible causes (if you change the power, then it must be radiation.)

I am interested in the pulsing repeating nature of the sound, can we have a longer listen perhaps do some analysis on the pattern?

 

[gemini86]

When i got there, another tech friend had already hooked his DSO to the wall outlet. I don't remember what the sampling rate was, but I'd rather try again with my analog scope, because it was difficult even to pick up a trace on the speaker output of the mesa boogie.

The noise has been there to some degree for about 8 years. It's only recently been getting more frequent and more powerful. It's. constant, but the intervals between the groups.of pulses are somewhat random.

I'll see if I can get a longer clip. My next step is to rig up a battery powered high gain amp to a spare guitar pickup I have and see if I can verify that it's air born and also kill the power to the building to eliminate that.

 

[Kingston]

My friend owns a studio in town and has had this noise show up on unbalanced gear, amps, etc. for some time now. Now it's gotten stronger and more frequent, and is bleeding into his balanced gear and everything in between. Any clue as to what it is and what to do about it???

https://soundcloud.com/thaddeus-moore/what-is-this-noise?utm_source=soundcloud&utm_campaign=share&utm_medium=facebook

I think look for a very stable record label now, and book these guys for a big break after about 20-30 years. Good luck.

 

[pucho812]

if you can hear it, then there is a way to measure it. 

 

[gemini86]

if you can hear it, then there is a way to measure it.

correct.

 

[Brian Roth]

Did the AM radio test reveal anything?

Bri

 

[gemini86]

The radio didn't seem to pick it up, at least not loud enough to hear over the station bleed through or noise.

Here's the recorded noise on an oscilloscope. This is after a high pass filter to remove hum.

https://docs.google.com/file/d/0B6s_klsk9wMDLXlZcERFVUFmQlk/edit?usp=sharing

 

[StaticRick]

Can't see the scope document.  It says I need permission.

A couple of thoughts:

1. Timing the pulses with a stopwatch, they appear to be 1 second apart.  This might lead me to investigate anything with a clock or timer in it, although the variation in the number of pulses is strange.  PPS (Pulse-Per-Second) signals are used by radio beacons and GPS.  Some GPS receivers will output a PPS.  I always assumed that they do this continuously, but they may not.  (http://en.wikipedia.org/wiki/Pulse_per_second)

2. Does the studio share the building with anyone else?  Could this be coming from something at a neighboring business?

3. If you can pick up the sound on something battery operated, try turning off circuit breakers until it goes away.  You may be able to isolate it to one circuit and investigate from there.  (If you can't do it with something battery operated, try turning off the breakers that aren't needed to monitor the noise.)

4. I think someone asked before, is there any correlation between the noise and time of day?  That might tell a lot, especially if it's an outdoor light trying to start.

I realize how annoying this problem is for you and your friend, I hope by tossing around ideas we can help.  It would be awful if he had to move his studio because of this mystery noise.

 

[bruce0]

StaticRick is right... they seem 1 second apart.  So I started doing some searches on the web for EMI pulses 1 second apart, and got some interesting links.  Searches with the terms RFI, EMI, HAM, and "1 Second" were useful.

Questions that arose are:  Is the noise temperature or weather dependant?  Is it time of day dependent (lunch hour? Closing time?).  Is it seasonal?

My bet is on electric fence.

Here are the results of my search:

Case 1:
Fence - Lengthy description but in summary: a consumer installed electric fence product, with an arcing section due to corrosion.  Has some good info on search technique.
http://www.qsl.net/n1lo/rfistory.txt

Case 2
Here is a document on searching for RFI (excerpts follow)
http://downloadfile.anritsu.com/RefFiles/en-us/Products-Solutions/RF-Interference-Hunting-Techniques.pdf

•  Electric fences
Electric fences generate a short pulse of high voltage then turn it off for a
second or two. This allows shocked animals time to move away from the fence
before it shocks them again.
•  Bakery ovens
Bakery ovens have high wattage heating elements, over 2,000 watts. The ovens
are typically regulated by turning the heating element on and off as needed
to maintain the desired temperature. This switching action generates impulse
noise.
•  Welding
This is a large electric arc that starts and stops every time the welder draws a
bead. Need we say more?
•  Electrical motors from elevators, floor buffers or even FAX machines
Many types of electric motors have brushes, which can create quite a bit of arcing and sparking. Have
you ever looked into the back end of an electric drill and seen the blue sparks around the brushes? 
That’s a good example of impulse noise caused by an electric motor.
•  Power lines, which may arc and spark
Have you ever been near a high voltage transmission line on a damp or foggy day? 
Enough said.
•  Light dimmers
Light dimmers operate by suddenly turning the AC power off part way through the power cycle of the
sine wave. This creates impulse noise. While these dimmers are filtered, filters may fail.

Case 3
Another HAM operator - with a list of suspects similar problem. No solution.
http://www.eham.net/ehamforum/smf/index.php?topic=56679.0

 

[bruce0]

You have a lot of cows!  In massachusetts we have 39000, In Oregon you have 1.2Million!

Here is a new zealand electric fence interference document.

http://www.rsm.govt.nz/cms/pdf-library/customer-support/5-step-electric-fence-interference.pdf

 

[gemini86]

Edited link so everyone should be able to see it now.

It does sound like an arcing noise. I've been around welders for years so I'm used to the jacob's ladder sound. This is within city limits, so there should be no electric fences nearby. The neighbors are a small bakery (it is owned by the studio owner and hasn't been there for half as long as the noise has) an insurance agency and a couple other small offices. There's a muffler shop a little further away, but the owner swears there's no battery charger or welder or anything that's on constantly to be making this noise at all hours of the day. There IS a pizza place across the street, it's been there a long time, but why would the nose suddenly get louder and more frequent?

I think I'll know more once I sniff it out with a battery powered unit.