  Scattering mechanisms in graphene are critical to understanding the limits of
signal-to-noise-ratios of unsuspended graphene devices. Here we present the
four-probe low frequency noise (1/f) characteristics in back-gated single layer
graphene (SLG) and bilayer graphene (BLG) samples. Contrary to the expected
noise increase with the resistance, the noise for SLG decreases near the Dirac
point, possibly due to the effects of the spatial charge inhomogeneity. For
BLG, a similar noise reduction near the Dirac point is observed, but with a
different gate dependence of its noise behavior. Some possible reasons for the
different noise behavior between SLG and BLG are discussed.
