  Current noise in nanoscale systems provides additional information beyond the
electronic conductance. We report measurements at room temperature of the
nonequilibrium "excess" noise in ensembles of atomic-scale gold junctions
repeatedly formed and broken between a tip and a film, as a function of bias
conditions. We observe suppression of the noise near conductances associated
with conductance quantization in such junctions, as expected from the finite
temperature theory of shot noise in the limit of few quantum channels. In
higher conductance junctions, the Fano factor of the noise approaches 1/3 the
value seen in the low conductance tunneling limit, consistent with theoretical
expectations for the approach to the diffusive regime. At conductance values
where the shot noise is comparatively suppressed, there is a residual
contribution to the noise that scales quadratically with the applied bias,
likely due to a flicker noise/conductance fluctuation mechanism.
