Excessive noise in signal, 8Khz hum

I recently helped someone set up some recording equipment remotely. They are in a different state so I cannot actually play around and maximize their settings. They are using a Behringer Q1202USB mixer which is hooked up to his PC with the USB cable. He has 3 Behringer C1 mics. His signal is relatively noisy and there is an 8khz buzz in the left channel and a 6khz buzz in the right channel.



He uses Audacity to record and then sends me the files to edit and I can do some cleanup in Audition but I would prefer to not have to clean it up as much. This is what his signal looks like. His input volume in Audacity is .6/60%.



http://ift.tt/1xk3Jqv



And this is what it sounds like http://ift.tt/1xk3L1A



And this is a picture of his settings. I use an Alesis Multimix 4 USB at work and a Behringer x1204 USB at home with similar settings and I do not get this much noise in the signal.



http://ift.tt/1L6FtUD



I do see I need to have him center his EQ knobs but that's not causing the noise. Any thoughts on what exactly is causing the noise and 6/8k hums?

Excessive noise in signal, 8Khz hum