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Tech: Removing 60 CPS Hum

Barbara Shaw 07 Nov 10 - 08:21 PM
Sandy Mc Lean 07 Nov 10 - 08:25 PM
GUEST,.gargoyle 07 Nov 10 - 08:46 PM
Amos 07 Nov 10 - 09:26 PM
Barbara Shaw 07 Nov 10 - 10:22 PM
JohnInKansas 07 Nov 10 - 11:06 PM
Richard Bridge 08 Nov 10 - 03:46 AM
Richard Bridge 08 Nov 10 - 03:48 AM
The Fooles Troupe 08 Nov 10 - 04:08 AM
Darowyn 08 Nov 10 - 04:29 AM
Leadfingers 08 Nov 10 - 04:31 AM
The Fooles Troupe 08 Nov 10 - 05:07 AM
Mitch the Bass 08 Nov 10 - 07:06 AM
Barbara Shaw 08 Nov 10 - 09:27 AM
s&r 08 Nov 10 - 10:14 AM
Richard Bridge 08 Nov 10 - 10:24 AM
Mitch the Bass 08 Nov 10 - 10:34 AM
Barbara Shaw 08 Nov 10 - 10:39 AM
s&r 08 Nov 10 - 11:23 AM
John J 08 Nov 10 - 11:32 AM
GUEST,punkfolkrocker 08 Nov 10 - 11:32 AM
GUEST,punkfolkrocker 08 Nov 10 - 11:32 AM
pdq 08 Nov 10 - 11:48 AM
framus 08 Nov 10 - 07:12 PM
Leadfingers 08 Nov 10 - 07:15 PM
GUEST,.gargoyle 08 Nov 10 - 07:36 PM
The Fooles Troupe 08 Nov 10 - 09:15 PM
GUEST,Rick 03 Dec 17 - 03:53 AM
GUEST,Ray 03 Dec 17 - 12:24 PM
Donuel 05 Dec 17 - 01:13 PM
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Subject: Tech: Removing 60 CPS Hum
From: Barbara Shaw
Date: 07 Nov 10 - 08:21 PM

Anyone know if this is possible? Any advice on how to remove it from a home recording?

We did some recordings using our studio mic and PA to go into the computer, and the result was a noticeable hum throughout the recording. Is there a way to remove this frequency via software while keeping the rest of the recording intact?

Well, at least I'm told it's a 60 cycle hum. Maybe it's just a hum. But without it, the recordings are really worth saving.


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Subject: RE: Tech: Removing 60 CPS Hum
From: Sandy Mc Lean
Date: 07 Nov 10 - 08:25 PM

Down load Audacity (free) and use the noise removal tool.


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Subject: RE: Tech: Removing 60 CPS Hum
From: GUEST,.gargoyle
Date: 07 Nov 10 - 08:46 PM

Having paid the price...
And messed around with Cakewalk and Sibelius and SoundForge...

What Sandy wrote is 100% on target and it is WINDOZE, AppleSauce, and soft cuddly Lynix platform.

Sincerely,
Gargoyle

Why pay a fee ... when the entire world is free?


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Subject: RE: Tech: Removing 60 CPS Hum
From: Amos
Date: 07 Nov 10 - 09:26 PM

SoundSoap is also a very useful tool for this and has a filter just for the 60 Hz band among others.


A


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Subject: RE: Tech: Removing 60 CPS Hum
From: Barbara Shaw
Date: 07 Nov 10 - 10:22 PM

I have Audacity and just tried it but the results were not good. I gave it a sample of "noise" and then had it remove that noise from the recording. It took out much of the guitar and mid-range of the vocals as well, which were apparently at that same frequency. Maybe I'm just not getting the sample from a good spot. Will keep experimenting.

Thanks for the suggestions.


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Subject: RE: Tech: Removing 60 CPS Hum
From: JohnInKansas
Date: 07 Nov 10 - 11:06 PM

"Sampling the sound" likely will pick up parts of other low frequencies that aren't really noise, so if you remove what looks like your sample you'll lose more than you want to.

I'm not familiar with the program, but if it has a specific "60 Hz remover" you're likely to have better results from using it. The 60 Hz power frequency nearly always is very accurate and stable, so a "narrow band" removal should be quite accurate.

(But I'm just guessing. One of our experts can probably be more specific.)

John


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Subject: RE: Tech: Removing 60 CPS Hum
From: Richard Bridge
Date: 08 Nov 10 - 03:46 AM

No way guitar or vocals are 60Hz. Bottom note on a bass guitar in standard tuning is about 80 Hz.

You need to take your noise sample from a place where nothing else is happening - nothing. Audacity takes that noise, reverses the phase, and thus cancels out that noise.

A 60Hz remover will take out everything at 60Hz (on a pretty narrow frequency band). If you have no drums or bass guitar it will probably work well.


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Subject: RE: Tech: Removing 60 CPS Hum
From: Richard Bridge
Date: 08 Nov 10 - 03:48 AM

PS - I once had a horrid gig where I was doing PA - a big deep but fluctuating hum. Turned out it was two things - noise on the mains from the ventilation fans getting into the power amps, plus physical noise from same fans getting into the kick drum mic.


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Subject: RE: Tech: Removing 60 CPS Hum
From: The Fooles Troupe
Date: 08 Nov 10 - 04:08 AM

I reckon one should kick drum mics right out of the place...


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Subject: RE: Tech: Removing 60 CPS Hum
From: Darowyn
Date: 08 Nov 10 - 04:29 AM

The problem becomes difficult because the mains hum (50Hz on this side of the Atlantic) is not the pure single frequency sine wave that in theory it ought to be. It contains several harmonics, the second one at 100 or (in the US) 120Hz falls right into guitar range, and the range of Bass Vocals.
If the mains hum is at a high amplitude, the peak of the wave may clip and extend the harmonic series right across audio frequency range.

A noise sampling noise reduction device will pick up frequencies of 2,3,4,5 times the mains frequencies and remove them all.
It will not sound good because it will leave big holes in the sound spectrum.
On the other hand, a narrow band filter will leave the harmonics in.
It will not sound good because the harmonics of the mains hum are still audible.
The only proper approach is to remove it at source, before you record.
You might be able to do it, but you'll have to accept that sometimes, it's never going to be worth the trouble.
Cheers
Dave
P.S.
Cycles per second are called Hertz (Hz) in international communications.


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Subject: RE: Tech: Removing 60 CPS Hum
From: Leadfingers
Date: 08 Nov 10 - 04:31 AM

Presence of a Mains Hum (UK Mains is 50Hz , USA is 60Hz) on a recording would indicate a dodgy earth somewhere to me ! It wouldnt do any harm to check that for future reference .


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Subject: RE: Tech: Removing 60 CPS Hum
From: The Fooles Troupe
Date: 08 Nov 10 - 05:07 AM

"If the mains hum is at a high amplitude, the peak of the wave may clip and extend the harmonic series right across audio frequency range."

And sadly, the frequency, although theoretically held stable, does wander about a bit... making it less effectively removed if the filters are offset by even a small amount, and the higher harmonics will thus be even further offset... also the amount of the harmonics varies over time too.

I still have a famous LP made in the 70s or thereabout of 'musique concrete' - it is just a recording of mains hum - and you would be surprised what you think you can hear in it ... :-)


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Subject: RE: Tech: Removing 60 CPS Hum
From: Mitch the Bass
Date: 08 Nov 10 - 07:06 AM

Whilst agreeing with the comments about harmonics of 60Hz being present, you may get acceptable results just filtering out the 60Hz with a notch filter or a High Pass Filter. A noise filter is meant for getting rid of hiss etc. not specific frequencies.

Unfortunately the lowest note on a 4-string bass guitar is 41.2 Hz (not 80 as suggested above) so you may lose notes around B(61.74Hz).

Audacity has an FFT filter and a High Pass Filter which may be sufficient but it also has a "Nyquist Prompt" which you can program to remove specific frequencies or you can download a notch filter plugin at http://audacity.sourceforge.net/nyquist/notch.zip.

Mitch


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Subject: RE: Tech: Removing 60 CPS Hum
From: Barbara Shaw
Date: 08 Nov 10 - 09:27 AM

I went back to an original track and found a few seconds of hum where nothing else was happening. Used that for the noise sample and then tried Audacity's noise removal on the mixed wav file.

It worked! At least to my ears. We'll see what the more discriminating ears have to say when they get home.

Mudcat to the rescue again!

P.S. But now I want to remix the tracks with different effects for GE and reverb, since that hum is gone. And people ask what the heck I do all day...


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Subject: RE: Tech: Removing 60 CPS Hum
From: s&r
Date: 08 Nov 10 - 10:14 AM

Best not to get hum in the first place. Because you used your PA and computer, it may be that the earth/ground connections for the computer and PA equipment are separate, and the various earth/ground connections form a loop which act as a sort of aerial to low frequencies.

Avoiding this is a bit of a black art:

Keep leads short
Use balanced good quality leads/connectors if possible
Don't plug items in at opposite sides of the room
Don't run signal and power cables alongside each other
Fluorescent lights are often an electrical noise source
Use ground lift only as a last resort
Listen carefully in the recording room for eg fridge noise, or central heating pump or W.H.Y.

I'm sure this list is not exhaustive...


Stu


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Subject: RE: Tech: Removing 60 CPS Hum
From: Richard Bridge
Date: 08 Nov 10 - 10:24 AM

I must be an octave adrift.


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Subject: RE: Tech: Removing 60 CPS Hum
From: Mitch the Bass
Date: 08 Nov 10 - 10:34 AM

"...the various earth/ground connections form a loop which act as a sort of aerial to low frequencies..."

I'm not at all sure that this adequately explains the operation of a ground loop. (This is what we call English understaement)


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Subject: RE: Tech: Removing 60 CPS Hum
From: Barbara Shaw
Date: 08 Nov 10 - 10:39 AM

What we finally did to avoid the hum during recording is buy a USB Dual Pre (preamplifier) which connects our studio mic directly to the computer. No hum. Cleaner sound and easier setup for sure although it sometimes acts funny with my sound card, cutting out and needing to have the devices reset when I unplug anything to listen via computer speakers rather than headphones, etc.

Stu, we did get some occasional noise (although no hum) even with this preamp, and your list is useful for us to check. I thought it might have been something electrical running in the room or elsewhere in the house, and you've given me several ideas to check.

I'm trying to get the hum out of previous recordings because the artist lives several states away and is unlikely to be able to re-record with us. More about these precious recordings when/if they are released.


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Subject: RE: Tech: Removing 60 CPS Hum
From: s&r
Date: 08 Nov 10 - 11:23 AM

Mitch- not intended as an explanation, hence 'sort of'. Reducing and removing hum is a black art.

Barbara - pleased to have given you some ideas and that you've solved the worst of the problem. Removing anything will affect other aspects of the recording - your ear is probably the best guide to how successful it is.

If you can't remove it completely to your satisfaction you may be listening for the hum; get someone else to listen to it. It could be better than you think.

Stu


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Subject: RE: Tech: Removing 60 CPS Hum
From: John J
Date: 08 Nov 10 - 11:32 AM

Is it possible to re-record - the next time making sure the screen to the microphone is earthed properly.

It may sound a bit of a contradiction, but sometimes it can be beneficial for the microphone NOT to be earthed. It's a bit 'suck it and see').

JJ


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Subject: RE: Tech: Removing 60 CPS Hum
From: GUEST,punkfolkrocker
Date: 08 Nov 10 - 11:32 AM

I still use CRT computer monitors

[every time i save enough £££S to buy a modern LCD flat screen
I get distracted and buy bargain guitar gear in a discount sale..]

so I expect to contend with a certain level of hum when recording
various single coil/humbucker electric guitars into my sound card.

At the moment i just shuffle round on my swivel chair
to get the optimum 'hum free' position
in relation to the monitor.


I've not got round to trying hum eliminating software yet.
How effective might it be in reducing hum that has been recorded
on a guitar tone with slap back echo and reverb..???

ie, any hum that could be 'sampled' from a track in between playing
has a bright reverb imprinted over it.

Maybe my only pragmatic option is to just remember to use
careful noise gate settings
every time I record something spontaneous.

I'm in the UK, so need specific advice regarding our Brit hum frequencies, thanks.

Also, even when i do finally aquire an LCD flat screen
for quieter hum reduced recording,
will these new 'green' energy saving light bulbs
be just as much a nuisance hum source
as old fashioned flurescent tube lighting ???


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Subject: RE: Tech: Removing 60 CPS Hum
From: GUEST,punkfolkrocker
Date: 08 Nov 10 - 11:32 AM

I still use CRT computer monitors

[every time i save enough £££S to buy a modern LCD flat screen
I get distracted and buy bargain guitar gear in a discount sale..]

so I expect to contend with a certain level of hum when recording
various single coil/humbucker electric guitars into my sound card.

At the moment i just shuffle round on my swivel chair
to get the optimum 'hum free' position
in relation to the monitor.


I've not got round to trying hum eliminating software yet.
How effective might it be in reducing hum that has been recorded
on a guitar tone with slap back echo and reverb..???

ie, any hum that could be 'sampled' from a track in between playing
has a bright reverb imprinted over it.

Maybe my only pragmatic option is to just remember to use
careful noise gate settings
every time I record something spontaneous.

I'm in the UK, so need specific advice regarding our Brit hum frequencies, thanks.

Also, even when i do finally aquire an LCD flat screen
for quieter hum reduced recording,
will these new 'green' energy saving light bulbs
be just as much a nuisance hum source
as old fashioned flurescent tube lighting ???


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Subject: RE: Tech: Removing 60 CPS Hum
From: pdq
Date: 08 Nov 10 - 11:48 AM

"It contains several harmonics, the second one at 100 or (in the US) 120Hz falls right into guitar range..."

Hum originating within the equipment is almost always power supply problems and is twice the "mains" frequency, either 100 or 120 Hz, rather than a harmonic of the power line frequency.

Actually, if you hear a 50 Hz tone in Europe (or Japan) or a 60 Hz one in the US, it is either induced into the system by proximity to power lines or by heavy current draw in equipment, such as the the fan motors mentioned.

Various grounding problems, either a "ground loop" or a weak ground point can cause gray hairs on a soundsman's head.

All filters, passive or active, degrade the fidelity. Period.

Best to fix the problem rather than put a bandaid on it.


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Subject: RE: Tech: Removing 60 CPS Hum
From: framus
Date: 08 Nov 10 - 07:12 PM

I'm just trying to thumb a lift on this thread.
I'm getting 50hz hum on my tv since I bought a wall bracket for it and had to buy an extension scart lead. There is an almost constant, but varying, mains hum. I'm fairly sure it is not due to the proximity of the lead to the mains feed and would welcome any suggestions (of a not too technical nature).
Thanks, Davy.


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Subject: RE: Tech: Removing 60 CPS Hum
From: Leadfingers
Date: 08 Nov 10 - 07:15 PM

Framus- That DOES Sound like a dodgy earth connection


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Subject: RE: Tech: Removing 60 CPS Hum
From: GUEST,.gargoyle
Date: 08 Nov 10 - 07:36 PM

When you have the desired output....save the file to a "histogram."



Sincerely,

Gargoyle



Like a "Christmas cookie cutter" you should be able to replicate even a "live Michael Jackson."


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Subject: RE: Tech: Removing 60 CPS Hum
From: The Fooles Troupe
Date: 08 Nov 10 - 09:15 PM


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Subject: RE: Tech: Removing 60 CPS Hum
From: GUEST,Rick
Date: 03 Dec 17 - 03:53 AM

Your TV had a slight hum (free standing). Just a slight vibration caused by ac/dc switching. Now your wall is acting as a piano sound board. It is not coming from your speakers. Using grommets and dense
rubber insulation strip/roll you can isolate the vibration from the wall and brackets.


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Subject: RE: Tech: Removing 60 CPS Hum
From: GUEST,Ray
Date: 03 Dec 17 - 12:24 PM

I hope that, seven years later, they've managed to sort it out.

The worst hum I ever had to sort out was in a large, posh, hotel in a big northern seaside town. I had my power amps plugged in at one end of the ballroom and and the desk plugged in at the other end. Could I get rid of the hum!

I eventually went to the reception desk and asked if they had a house electrician. He came down, scratched his head and was similarly puzzled. This end of the ballroom is on the same phase as the other end I asked? Hmmm .... I don't think it is. Problem solved!


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Subject: RE: Tech: Removing 60 CPS Hum
From: Donuel
Date: 05 Dec 17 - 01:13 PM

Gargoyle, As intimidating as I found cakewalk and sibelius and other software I salute you for venturing forth. I went to Chuck Levins music store and they sold me a little plug in box that got rid of all the hum from my amplified Korg. ?


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