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periodic 60 cycle hum

 
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Foog
DC


Joined: 27 Oct 2013
Posts: 608
Location: Upper Canuckistan

PostPosted: Thu Aug 21, 2014 11:12 pm    Post subject: periodic 60 cycle hum Reply with quote

Not sure if this is really a gear question, but what the heck...

I've been getting what I'm pretty sure is a 60 cycle "electrical" hum coming from... well, I can't quite pinpoint it. I'm 100% sure it is not coming from any of my recording gear, or anywhere from within the room I record in, but other than that I can't quite isolate whether it is coming from my wiring, fuse box, or even outside. To make matters even odder, it is irregular and periodic. It only occurs at night, and not every night nor all night. It's disconcertingly loud when it does happen, so I ain't too pleased about it. But I am going to start phase 2 of the booth upgrade this weekend (that's right Lee, the race is on!), which should isolate my recording space enough to eliminate the problem, so I'm not losing sleep over it at this point.

Still, the curiosity is driving me mad. What could be the cause, irregular and nocturnal as it is? Anyone have any ideas?
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Rob Ellis
M&M


Joined: 01 Aug 2006
Posts: 2385
Location: Detroit

PostPosted: Fri Aug 22, 2014 7:17 am    Post subject: Reply with quote

what's your signal chain?
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dwpthe3rd
Contributore Level V


Joined: 28 Feb 2010
Posts: 198
Location: Where palm trees meet pines

PostPosted: Fri Aug 22, 2014 8:21 am    Post subject: Reply with quote

If it's indeed a 60hz 'electrical' hum affecting your signal chain, I doubt that any amount of booth isolation will solve this problem - booth will isolate airborne noise(s).

Dave
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Foog
DC


Joined: 27 Oct 2013
Posts: 608
Location: Upper Canuckistan

PostPosted: Fri Aug 22, 2014 9:23 am    Post subject: Reply with quote

Sorry, I should have been clearer in my original post. It is not affecting my signal chain. (the chain itself is fairly simple: microphone ---> tube-equipped-but-not-a-preamp microphone power source --> Mbox mini ---> MacBook Pro)

This electrical hum isn't a buzz I hear on my headphones, or the kind of signal interference hum you get when plugging a guitar into a poorly grounded amp. Instead, it is a noise I hear floating about the room and the rest of the basement late at night sometimes. As if I had Cicadas. Digitized and auto-tuned cicadas somewhere!

I can never quite isolate it. Is it coming from my fusebox or wiring? The walls? Outside perhaps? I dunno. I hate not knowing!
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Bruce
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Joined: 06 Jun 2005
Posts: 7921
Location: Portland, OR

PostPosted: Sun Aug 24, 2014 10:53 am    Post subject: Reply with quote

For an ambient hum I'd check for small motors that might be running elsewhere in the house, such as small fans on appliances or in the ceiling, water pumps, refrigerators, refrigeration, sump pumps, exhaust fans.

If a careful listening campaign around the house doesn't turn up the source then go to the breaker box and turn off a circuit and go back to your space and listen. Do that one by one until you've at least narrowed it down to a part of the house.

If that doesn't work check for amorous racoons under the house.

B
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Bish
3.5 kHz


Joined: 22 Nov 2009
Posts: 3738
Location: Lost in the cultural wasteland of Long Island

PostPosted: Sun Aug 24, 2014 11:12 am    Post subject: Reply with quote

Motors are a good call... and the compressors on refrigerators and freezers and be very noisy sometimes. I'd also add transformers to the list.

Here's an interesting article on transformer noise. And here's another one.

A transformer may be acceptably quiet most of the time, but slight variations in voltage or frequency (within the parameters of your supply) may set up vibrations. Street supply is not as clean as we would expect.
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Bish a.k.a. Bish
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vkuehn
DC


Joined: 24 Apr 2013
Posts: 688
Location: Vernon now calls Wisconsin home

PostPosted: Sun Aug 24, 2014 12:01 pm    Post subject: Reply with quote

Foog wrote:
Sorry, I should have been clearer in my original post. It is not affecting my signal chain. (the chain itself is fairly simple: microphone ---> tube-equipped-but-not-a-preamp microphone power source --> Mbox mini ---> MacBook Pro)

This electrical hum isn't a buzz I hear on my headphones, or the kind of signal interference hum you get when plugging a guitar into a poorly grounded amp. Instead, it is a noise I hear floating about the room and the rest of the basement late at night sometimes.


Good clarification. I considered posting a request that you give us an audio sample. I sometimes hear people describing something as an AC hum that when I hear it... is not at all what I think of as AC hum.

Around my own house, things that have made noise that attracted my attention: Transformer for door-bell system. Little pump on water-heater that circulates water around the house so you always get hot water. My neighbors new AC unit that is otherwise much quieter than machines from the past. Ballast in a ceiling mounted florescent light fixture. TINY ballast in a small florescent READING lamp. Cable system set-top box. Ice maker in the fridge that is mulling over the idea of ejecting ice cubes nearing the end of their gestation period.
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Foog
DC


Joined: 27 Oct 2013
Posts: 608
Location: Upper Canuckistan

PostPosted: Sun Aug 24, 2014 7:48 pm    Post subject: Reply with quote

vkuehn wrote:


Around my own house, things that have made noise that attracted my attention: Transformer for door-bell system.

I had no idea doorbells could have transformers in them. My ignorance of electricity and electronic motors/devices is encyclopedic in scope, but mayhaps my noise source is indeed an errant appliance or gizmo with a transformer or somesuch in it.

Ah well. 'Tis all moot, since I have now begun working on the new and improved vocal room which will no doubt keep the entire world out perfectly while making me a wealthy and in-demand voiceoverist. Why, I think it might even help me shed a few pounds and be less awkward socially. Or at least have brightly coloured walls. (note to self: buy paint)
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ccpetersen
With a Side of Awesome


Joined: 19 Sep 2007
Posts: 3708
Location: In Coherent

PostPosted: Mon Aug 25, 2014 1:48 pm    Post subject: Reply with quote

Sort of on-topic, but we were doing a greenscreen session at the studio the other day and kept getting a disturbing hum through the mic. Checked the mic batteries, connectors, nothing wrong there. Finally figured out (after much plugging and unplugging of stuff) that the external power supply for the video camera was supplying the hum. So, we did the session on battery pack.
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yarg28
Been Here Awhile


Joined: 25 Aug 2014
Posts: 267
Location: Indiana

PostPosted: Tue Aug 26, 2014 6:29 am    Post subject: Reply with quote

Doh, Bruce beat me to this! "sound" advice though :p
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Start turning breakers off one at a time and see if you can isolate it to a circuit. If you cant then its probably nothing that you have control over.

If its a breaker you dont need while recording then there's a quick fix until you can hunt it down during unpaid time.

good luck.
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Foog
DC


Joined: 27 Oct 2013
Posts: 608
Location: Upper Canuckistan

PostPosted: Sun Aug 31, 2014 8:31 pm    Post subject: Reply with quote

Mystery solved!

Turns out it was a bedroom window fan in my bedroom, on the second floor of the house. It had a sneaky one-two punch of properties: a) it was VERY close in frequency to the typical 60 cycle "electrical" hum we all know and hate (though now that I know what the source is, I notice the giveaways that the sound is mechanical and not electrical after all, like a slight wavering or phasing or somesuch that electrical hums lack ...and b) I'm betting it is at a resonant frequency of the house frame or duct work or something. Shockingly present all the way down in the basement!

At any rate, not only have I managed to track it down (thanks for the advice, everyone!), I am pretty confident that when I finish building the new boothroom (TM) it will not be audible inside.
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vkuehn
DC


Joined: 24 Apr 2013
Posts: 688
Location: Vernon now calls Wisconsin home

PostPosted: Mon Sep 01, 2014 6:35 am    Post subject: Reply with quote

I love a mystery! Thanks for reporting what you found. And.... when you finish the new booth, it will be interesting to hear your report then. Vibrations like that just seem to shake an entire building don't give up easily!
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