Usually usb mics give a little bit of static when you record. Two things are going on when you have noise, a hum is the frequency interference of the power source you are using, static exists in all microphones at a certain volume. Good mics and audio interfaces have to be turned up awfully loud before static becomes noticeable but on usb microphones the interface is not always designed the best. If you are hearing hiss or static the problem is the audio interface being used in the mic itself. you could either have a bad copy of your mic or it simply might not be well designed. The mic itself always picks up noise, the sounds coming from the artist in front of it along with alot of other rf interference. Hiss is rf interference being picked up by the circuitry or cables somewhere along the way. Hiss can only be fixed with shielding. If you are hearing a hum sound you can only fix that by cleaning up the power source. The only real way you could do that is by plugging into the back of the computer where the ports are grounded better(on some cases with plastic front panels.) There is a big difference in between the usb audio interface which actually processes the audio on its own, and it uses completely digital signals which is why it is a very clean signal. A usb mic is not a digital signal in a less expensive model until it gets to your computer where you computer processes what is coming from the mic. On the way over there is alot of room for rf interference. For proof ask any electric guitar player and they'll tell you that they can get radio stations with there cables when they plug into an amp. The final thing that might be going on which happens with alot of budget priced usb mics is that the signal is artificially boosted and everything that the mic is picking up is also amplified including rf interference. all mics pick up hiss it';s unavoidable when you have metal parts and cabling plugged into an amp good designed setups minimize this effect.
I get a noise free setup by using a Digital audio interface, all digital output to monitors, mic cables shielded, and all of my equipment is plugged directly into to a grounded source. I could make it even better by using a power conditioner.
Three things to consider are your cables shielded, is the mic a good design free of interference, and is your power source clean.