CyFlow® Cube Instrument Operating ManualRev018_2012-01-278/36… background in a histogram?Histograms sometimes show undesired signals in the lower channels, frequently called ´noise´ or´background´. These signals may originate from cell fragments or other particles resulting from samplepreparation. In case of high signal amplification, background can also be caused by particle contaminatedsheath fluid.The lower level (L-L) or threshold?The lower level (L-L) threshold is a mean to suppress background signals. Signals below the lower level arerejected from the signal acquisition. To exclude noise from a histogram already acquired, a region-gate canbe used.