I hate to have to tell the OP this, but a noise gate isn't going to help with the hum, because technically "hum" isn't background noise, it's electrical interference. You're either going to have to find the source of it, and kill it (figuratively of course) or you're going to have to become very proficient at notching it out with an EQ and then hope that your notch is narrow enough to leave the remaining audio in decent shape.
 
Edit: Since you seem determined to use a USB mic, have you tried recording to your machine while it is unplugged? Unless of course you're using a desktop...I use a laptop, which can of course run on battery. Most "hums" are caused by AC and aren't as prevalent from DC in my experience.

The question is what frequency is the humming sound? Might not be 60Hz as some may think here. If it's higher than a steep notch may work too without effecting the voice too much.
 
USB microphone not the way to go, they are rather useless actually. I mean in this case it is generating an unwanted sound.
 
A downward expander might be better on voice so that even low level nuances will still get through. A gate can be a bit hard in its operation. It is still a band aid approach though. The humming sound should not be there to begin with.
 

I started to try the EQ but learned that no matter what I do while recording, it makes no difference. I've put the volume up, the gain up, tested all sorts of options with EQ, but nothing changes. 
 
What am I doing wrong? What do I need to do in order to get these changes to actually work while recording?
 
thanks.

The DAW records tracks dry. Software effects can only be applied after recording.

wow. so I can't set the volume levels or gain levels or anything else before recording so that the raw recording is louder?
 
 
 

The level is set at the interface. Here is the signal flow diagram http://www.cakewalk.com/D...amp;Req=Mixing.07.html

I can't get a single video for this so I'm supplying two:
 
Please check out this video on Quadcurve EQ:
http://www.youtube.com/watch?v=OxFBthlcTfs
 
then here's how to notch with another EQ:
http://www.youtube.com/watch?v=oOzqdbyAvyY
 
Please see if this helps with the Quadcurve.

Oh and this:
http://www.groove3.com/str/player_flash.php?id=4658&productid=16447
 

scook
The level is set at the interface. Here is the signal flow diagram http://www.cakewalk.com/D...amp;Req=Mixing.07.html

Right, and is a very important concept. The OP has to consider that Sonar can't control the level before it hits the A/D converter. If its too loud at that point its too late to fix later. You have to adjust the level at the source. 
 
 

trailblazer
wow. so I can't set the volume levels or gain levels or anything else before recording so that the raw recording is louder?
 
 
 

You have to understand that the signal coming into the computer is controlled by the device it's coming from.

It doesn't change the fact that you have to find out what's causing the hum. Quality recordings start with quality signals being recorded. If a stage of that chain is broken in some way then like any chain, it will on lynx be as good as it's weakest link.

You can certainly raise the level of the signal but any inherent flaws will also be raised. That's actually your complaint. There's a hum which may not sound very loud but by the time you record and raise the level of your signal you will invariably increase the noise as well. That's why folks go to such extraordinary lengths to get a clean signal.