I've had a blue Yeti microphone for a couple years now and I've pretty much never managed to use it for any real project because I'm unable to do anything about the background noise which is just too off-putting. I've tried literally everything an internet search suggests (quieter computer, different locations, avoiding fans/air conditioning etc etc) yet I can't seem to do anything about it. I haven't tried using a power usb hub but given that I've used many different types of computer to no effect I assume it doesn't make much of a difference. Is the level of background noise in this clip normal for the Yeti and require noise reduction in software or is there something I'm missing? What could be causing it? I assumed computer fans but I've tried placing it far away from the computer (a macbook pro that doesn't make much sound anyway) to no avail. Audio sample - http://vocaroo.com/i/s1zoLggEDBIY
I suspect that the 1kHz tone might be a DC-DC converter and/or insufficiently filtered noise from the +5V USB rail. The specs talk about "14mm condenser capsules". The price tag would suggest electret condensers (which could be operated at a nominal voltage of +5V, requiring very good decoupling from the digital ground and supply rail). If they use true condensers instead, a DC-DC converter is mandatory and they could just be operating it at data sheet conditions without checking its operating frequency to be outside of the audible range.
Which would be a real blunder. So my main candidate for the problem is that your mic does not separate the analog and digital power supplies sufficiently and that the operation of the USB communication makes more of an impact on the analog power than desirable.
Note that all this is technology that various manufacturers have managed to get under control in external soundcards and/or USB mics.
But good mics with good noise ratings tend to be phantom-powered and still are in a similar weight-size-and-complexity class as the Yeti, and handheld recorders with optional external mic inputs tend to have similar problems when providing phantom power. External USB soundcards are about the size where this sort of power/bleedover/DC-DC problem is solved well enough not to be bothersome.
So this is tricky and requires outside-the-box thinking and circuitry. Which usually is visible in the price tag.
Unfortunately that's just how it is with the Yeti man. You can't get rid of that background noise even with no gain. The Yeti's preamps are cheap, that's just about it. I use it for my personal projects and for streaming. If you want to record professional quality voiceovers without noise, you need to do your recordings in a treated room with a decent preamp+mic combo. And remember, it's useless to have a great microphone with shitty preamps.
This is 50 or 60Hz noise. It have a name "ground loop". Try to use ferrite cores for your USB cable or/and USB noise filter.