The CDJ-350 doesn't show two-decimal accuracy, so the unit will show 128 but it could be anywhere from 128.00 through 128.99. You may find you can adjust the slider through a couple of different pitch percentage points while the display remains at 128. This is perfectly normal.
You may be hearing noise because of your computer's USB chipset. If it is not properly isolated it will send interference through to the CDJs which I presume are being used as sound cards for your audio output. Another possibility is that you may try disconnecting the wall power for your laptop - if the noise disappears it was the charging circuit in your computer causing the noise.