Ceiling grid causing buzz in recordings


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Old 05-04-16, 11:34 AM
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Ceiling grid causing buzz in recordings

I'm hoping this is the right forum to post this question.
I'm trying to set up a home recording studio to do voice overs and narration.
I'm having a problem that shutting me down.
I have nasty buzz in my recordings.
Through trial and error I've discovered that it seems to be related to the ceiling tile grid. If I move the mic closer to it it buzzes louder.
I have found at least one 'dead' spot where I don't get the buzz. It's in the middle of the room by a support brace. I just can't record from there.

I'm suspecting that it's electrical in nature because it sounds like an AC hum to me. Can anyone give me a clue as to where to start to resolve this?
 
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Old 05-04-16, 12:08 PM
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First I'd make sure all your recording equipment is connected to properly grounded receptacles. Then I'd try grounding the grid (assuming you have metal grid). If you have copper water pipes they should be grounded and you could run a jumper wire from the grid to that as a test. If you don't have copper plumbing you could run a test jumper from the round ground terminal of an electrical outlet.

Problem is, the grid is usually painted which means all the little pieces may not make good contact with each other, so all the pieces may not get a good ground from one connection. But it is worth a quick test.
 
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Old 05-04-16, 12:26 PM
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Do you have fluorescent lighting troffers, CFL or LED cans suspended in the grid? If so, those are the by far the most likely source.
 
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Old 05-04-16, 01:12 PM
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Thank you for your responses.

I have CFL lighting.
I thought it might be the lighting so I turned off all the lights and tested. The buzz was still there.

I did check the grounding of the outlets early on in my troubleshooting with an outlet ground tester. It checked OK.

I have copper pipes. I see the house ground is fairly close to the grid so it shouldn't be too difficult to ground the grid.

Thank you.
Ralph
 
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Old 05-04-16, 11:24 PM
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At first I thought you were picking up the buzz from the fixture ballast but you still have it when the lights are off. A grounded or ungrounded grid should not affect your recording.

I have a sound company and have built studios. All you recording equipment should be on one circuit.... if possible. Grounds loops thru sound equipment is very common in this business.

Are you using all balanced 3 pin audio connections.... especially in the mic line ?

I have a good friend that is heavy into pro voice over work.... if you're interested let me know.
 
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Old 05-05-16, 06:12 AM
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My recording set up is really quite simple at the moment.
1 PC,
1 mixer board
1 Steinberg interface
1 XLR mic

Everything runs off the same outlet.
One of the test I did was to run everything off of my UPS without it being plugged in to see if that made a difference. It didn't.

The only thing that I found that made any difference at all was when I discovered if I move the mic closer to the grid it would get louder. Then I found I could find a dead zone where there was no buzz at all.

I did wonder if there was a filter I could install on the AC but I can't see how that would make a difference.

~Ralph
 
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Old 05-05-16, 07:51 AM
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Can you give it a try on UPS power with your main breaker off (all power in the house off)? This will at least eliminate or confirm the house power as a potential cause.
 
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Old 05-05-16, 07:59 AM
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I don't know if this is it, but I had a photo sensor for lights that would cause a buzz in the radio. changed sensor to another brand and buzz stopped. sensor was not anywhere near radio and not on same circuit.
 
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Old 05-05-16, 08:08 AM
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Thank you for the input.
I don't have any photo sensors so that couldn't be it.

Pulling the main breaker is an option. I'll have to reset a lot of thing (which will bug the heck out of my wife.)
That's something I'll have to schedule.
Or how about this: I leave main breaker on and turn off all the other breakers?
That way I could turn them on/off one at a time to see if I can narrow it down to where in the house it may be sourced from.
If it still buzzes after that I may have to hold an exorcism.
 
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Old 05-05-16, 08:52 AM
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Have you tried grounding the grid yet? It will not be the source of the interference, but it can act as an antenna and re-radiate the interference from another source.

Turning off all the power would be a good test. Wait until your wife goes out and tell her there was a power failure. You have my permission to omit the detail that you caused the power failure

Battery chargers are another notorious source of weird interference, especially the chargers for power tool batteries, but even smaller ones like for phones, shavers, and the like. They almost always use switching power supplies and often are poorly filtered to save size and cost.
 
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Old 05-05-16, 09:51 AM
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Then I found I could find a dead zone where there was no buzz at all.
What's different about the dead zone besides that it's dead?

Are any of your neighbors Ham Radio operators? I had a problem like that in the 70s. The broadcast was interfering with my turntable. When I played a record, I would hear muffled speech.
 
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Old 05-05-16, 10:13 AM
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I don't have any photo sensors so that couldn't be it.
Security lights, post lamps, dimmers, occupancy sensor light switches, motor speed controls...many use the same type of noisy power switch ("triac").

But I'm betting your hum is mechanical. A suspended ceiling is a gigantic "diaphragm" that can make a lot of sound from a minute vibration. Could be a fridge, noisy little doorbell or furnace transformer, traffic outside...
Are you using headphones or monitors to sync your voice-over? Could be acoustic feedback exciting a resonance in your ceiling (you didn't say whether your mic test was in a quiet room, or during playback).
 
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Old 05-05-16, 12:06 PM
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Do you have a 'cheater' (ie: 3 prong to 2 prong adapter) you could try on your power strip that you are running the equipment on? Just a test to see if taking the ground out would eliminate the hum.

I had the same problem when I'd want to connect my laptop to my stereo receiver via RCA jacks - 60hz hum. Unplugging the charger would eliminate it, and later found about ground loops and a cheater fixed it.

However, using a metal mixing board, you might not want to eliminate the ground as a permanent solution.
 
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Old 05-05-16, 06:47 PM
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So you're running the mic into the mixer then to the interface and then to your PC.

What are you using for a mic and mixer ?
Have you tried just the mic to the mixer ?
Have you tried a different mic and cable just to the mixer ?

If you had mechanical buzzing noises you should be able to hear them in the room.
It sounds to me like no ground to the mic.
 
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Old 05-16-16, 07:28 AM
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Here's an update to this:
By chance I happened to need hearing aids and I picked them up last week.
These hearing aids have a "Telecoil" mode that is supposed to be useful in places that have a wired loop. Auditoriums, Theaters, etc.

I was playing with the hearing aids and happened to switch it to Telecoil mode while sitting in my living room. Sure enough, I heard the buzz. Knowing that I still had the buzz if my main breaker was turned off I stepped outside and I still had the buzz. Wandering around my neighborhood I found that most of my block has it. At the end of the street(s) it's clear. Some areas are worse than others. There's a section in the lot next to mine where it's really bad.

I've tested other areas around my town and this is the only place I've found it so far.

We don't have overhead wires anywhere, it's all buried. I'd have to believe now that it's a issue with the utilities but I've no idea what. I'm not even sure how to pursue it with the electric company. How would I report a "buzz" in the neighborhood?
 
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Old 05-16-16, 09:02 AM
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60hz hum/buzz is everywhere. You can't stop it unless you get away from all AC wiring.
Your equipment is shielded to eliminate the noise.
 

Last edited by PJmax; 05-18-16 at 10:00 AM. Reason: typo
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Old 05-16-16, 09:23 AM
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The only place I get it though is in my own neighborhood.
I haven't found it anywhere else.

Is there someway I could shield my microphone from it? At least that way I could shield a room so I wouldn't have to deal with the problem.
 
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Old 05-18-16, 05:21 AM
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I am an expert at this. Check all of the following:

- First check out your mic very carefully. The mic or mic transformer should be wired to XLR pins 2 and 3, but NOT to pin 1. Pin 1 is ground for the case, and is the return if phantom power is used. Any connection between pin1 and either pin 2 or pin 3 renders the mic unbalanced and susceptible to hum or buzz.

- Next check the XLR cable for continuity pin 1 to pin 1, pin 2 to pin 2, and pin 3 to pin 3. Also check for shorts between pin 1 and pin 2, pin 1 and pin 3, and pin 2 and pin 3. All three lines must have continuity and there mist be no shorts.

- Check your mixer XLR input. Make sure it is really balanced, and no0t just "impedance balanced".

- Make sure all of the magnetic shields are in place on your microphone. Ditto for guitar pickups.

- Look for ground loops. This is any place where two cables connect the same two pieces of equipment together (such as insert and return lines. You can buy ground loop eliminators to put in signal lines where a ground loop exists.

- If you have a direct box, make sure it is not next to a "wall wart" power supply. It picks that up quite easily.

build a Faraday shield. Get some copper screening and put it above the suspended ceiling. be sure to ground it.If necessary, surround the studio on other sides.

All of the above are ways that noise can get into your audio system.

This alone may cure the problem.

Now for some detective work in the surroundings. Look for the following:

- dimmers in use anywhere in the house
- brush-type electric motors (e.g. power tools)
- electrostatic air filters
- ion air fresheners
- static electricity in the furnace blower belt
- fluorescent, neon, mercury vapor and other metal vapor lights, especially ones that are malfunctioning
- high tension wiring with damaged insulators
- LED and CFL light bulbs
- large electric motors
- greenery in the power lines
- a large electrical substation
- energy leaking from a computer (especially if the cover is off)
- welding or medical equipment
- defective TV set or computer monitor
- certain aquarium pumps
- radio or TV station
- cell phone tower
- Your own cell phone might be causing the buzz
- a traffic RADAR installation (vehicle detector or speed enforcement)
- airport RADAR
- a surge pr4otector power strip going bad
 
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Old 05-18-16, 06:41 AM
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The only place I get it though is in my own neighborhood.
I haven't found it anywhere else.
Radio amateurs over the years have developed special methods for tracking down interference. Power companies have done the same. Utilities may use ultrasonic devices for searching for arcing on poles and pad transformers. Hams use a variety of frequency receivers, usually AM, along with direction finding antennas.

Hams have their own short list of common offenders:
*plasma TV
*grow light ballast
*bad lightning arrestors on poles
*bad clamp connections to utility transformers
*solar panel controllers
*high efficiency wall-warts

You MIGHT be able to drive around with a portable AM radio, tuning off channel, and get pretty close to the offender. Better than a car radio, since a portable will have some directionality to its antenna.
 
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Old 05-18-16, 06:44 AM
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MidiMagic,
Thank you so much for responding. You put a lot of time into your response for me. Thank you.

A little bit on what I've done so far.
I've tried two different XLR cables.
I've killed the power to the house and ran off a laptop so I'm pretty sure it's not anything in the house creating it.
(I'm not sure how to check the Mic. It's an EV brand mic so it should be good quality.)

What is a "Wall Wort" power supply?

All the power in my neighborhood is run underground. There are no manufacturing facilities in the area and no cell phone towers.

I tested my cell, not it.

In one of my earlier post I noted that that week I got new hearing aids. These have a Telecoil option. I've found that if I put them in telecoil mode I pick up the same buzz as my mic. I then took a walk through my neighborhood. The only place I didn't pick it up was at the cul-de-sac. It was stronger or weaker depending on where I stood. I noticed that in the back of my lot it's very strong. A the front of my lot it's there but not as strong.

Our power for the neighborhood is buried. I'm pretty sure it runs through at the back of our lots.

At this point I'm convinced that the buzz is sourced with the power through the neighborhood. I just don't know what I can do about it. Someone suggested that I call my public service commission at our state capitol and ask what could be done about it. I'd like to make that my last option.

I have thought about a Faraday shield. Thanks for re-enforcing what I was thinking. As a test I was thinking I could take a cardboard box, cover it with tinfoil and then ground that. It that works then I could build something more permanent. Would you think that would be a fair test?

Ralph
 
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Old 05-18-16, 06:54 AM
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Good thought. But do people actually own portable AM radios anymore?
I'll have to see if I can beg, borrow or steal one from someone.

Ralph
 
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Old 05-18-16, 07:53 AM
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I have a portable AM-FM-Weather radio...somewhere...maybe its... Now I'm going to have to look for it and see if it still works.
 
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Old 05-18-16, 09:53 AM
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Furd; don't bother, the dry cell batteries have leaked all over by now.

Here is one story of finding a utility issue; in this case, above ground. I have RFI, now what- Locating it - NK7Z.NET

A problem with radiation out of a house usually has less long range effects than a utility defect, but still can cause a few blocks worth of interference.
Walk around some of your pad mounted transformers, those green steel boxes. See if you can find the strongest offender. That could point to a house fed from that box, or the box itself. You might get real lucky and hear arcing.
 
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Old 05-18-16, 10:04 AM
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I've killed the power to the house and ran off a laptop so I'm pretty sure it's not anything in the house creating it.
You cannot directly connect a balanced XLR type mic to a laptop. So how are you testing the system on laptop alone ?
 
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Old 05-18-16, 10:27 AM
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Furd; don't bother, the dry cell batteries have leaked all over by now.
Actually, they are just fine. The radio was right where I thought it was and when I turned it on I heard the weather report.

But thanks for the reminder. I've "lost" enough equipment due to leaking batteries that I usually don't leave them in place. I took the batteries out and left them right next to the radio.
 
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Old 05-18-16, 09:08 PM
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What kind of connector are you using to connect the XLR cable to the laptop?

I thought you were using a mixer with balanced XLR mic inputs. If you do not have this, you are going to have buzz.

Most of the XLR-to-other-connector adaptors you can buy destroy the noise reduction power of the balanced line. Some of them even leave one side of the mic open. Either way, you have a hum antenna.

You need a proper balanced to unbalanced matching transformer. A direct box will do.

Any boom box is a portable AM radio.

I have a portable radio that has this line in the instruction manual:

"Do not lose this radio in closet while installing dead batteries/"
 
 

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