Sounds like light dimmer buzz.

Ty Ford

If both tracks are from the same source (ie. you double the SAME mic track for mixing) and you are VERY careful in placing both tracks in your timeline AND you don't add any modulation or time based effects, they SHOULD remain perfectly in phase.

Great...every room in the house...sorry studio has dimmers in them. These were not on in the room where the mic was set up mind, but likely in the room where the desk and feed was in. I thought I'd checked everything too (mobiles were turned off etc).
So, might there be a chance I can somehow electronically eradicate this? Soundtrack pro/freq filter within logic?

Cheers.

Yes - fortunately the snap function is on so no danger of misplacing on timeline. Compression and reverb ok to add when doubling up?

Thanks.

Dimmers
 

Yes, it sounds like 50 Hz square (ish) wave. That's the trade mark of domestic lamp dimmers, which goes away when the light is turned up to full. The good news is that as it is relatively stable, you can invert the phase of a good sample of buzz alone. Then you stand a good chance of cancellation. These cursed dimmers are even more of a pain on film sets, where instead of the dear old rheostats, which reduced the voltage and preserved the wave form, they chop the top and bottom of each cycle. Lighter in weight, cheaper to make, but sound like a hive of demented bees. And woe betide you if you lay an audio cable anywhere near the dimmer or its cable.

Aye...I can't stand bright lights in the house, hence we're full of halogens on dimmers (perhaps I should sway towards LED's eventually, for 'green' reasons and all that).
But they do buzz somewhat.

I'm not entirely sure how I would begin to invert the phase of the buzz however - doable in soundtrack pro?

I'll know next time...table lamps from now on when the 'live on air' light is red!

Cheers Nick.

I think from the frequency wave (in STP) this then is fairly evident (if it's the central band running throughout the entire waveform):

David, I notice a couple of points in the posted timeline/waveform where there is ONLY background noise. Try this:

Carefully select just a section of "noise"
In the Process menu select Noise Reduction > Set Noise Print
Select the entire wave form
In the Process menu select Noise Reduction . Reduce Noise and play with the settings until you've eliminated or lowered the 50Hz noise floor.

WARNING: Overly aggressive use of the Noise Reduce function MAY cause mosquito style artifacting which in some cases is WORSE than the 50Hz hum.

Hi Shaun, I just happened to be playing with Noise Reduction in Soundtrack Pro...and it's working quite remarkably. Not sure yet at what level the db noise reduction should be set at (defaults at -60db which is just about right...a slight buzz is left but it's almost perfect.). I haven't tried the Set Noise Print route yet, rather selected the whole waveform (or parts when first testing) then clicked on apply. There seems to be a slight, almost negligible degradation of the vocal performance...although I'm almost convincing myself there is one rather than it being obvious.

I guess I can then send this back to Logic and apply compression (double tracked), EQ if required and the odd effect (again if required).

Still like to work out the method for inverting the phase mind. The DC offset, Power line hum analysis in STP didn't seem to do anything, rather strangely??
I'll post a before and after quick sample of the Noise reduction and see whether you folks think the vocal has been lightly 'stripped' of something.

Many thanks.