I use Windows 7 Professional. I have set up a mic and preamp via USB. Whether I use the Windows sound recorder or Audacity, there is a low level white noise which is enough to notice. In the course of trying to solve the problem, I have had my computer and all accessories and software checked at a good computer shop with no causes found there. I also engaged in an extensive discussion on Audacity forum, which found no solution. I've been told it "should" work. The current opinion from the computer shop and the forum is that there is some setting or configuration in Widows that needs to be corrected. What might I check?