  The electrical current noise of a quantum wire is expected to increase with
increasing applied voltage. We show that this intuition can be wrong.
Specifically, we consider a single channel quantum wire with impurities and
with a capacitive coupling to nearby metallic gates and find that its excess
noise, defined as the change in the noise caused by the finite voltage, can be
negative at zero temperature. This feature is present both for large ($c \gg
c_q$) and small ($c \ll c_q$) capacitive coupling, where $c$ is the geometrical
and $c_q$ the quantum capacitance of the wire. In particular, for $c \gg c_q$,
negativity of the excess noise can occur at finite frequency when the
transmission coefficients are energy dependent, i.e. in the presence of
Fabry-P\'erot resonances or band curvature. In the opposite regime $c \lesssim
c_q$, a non trivial voltage dependence of the noise arises even for energy
independent transmission coefficients: at zero frequency the noise decreases
with voltage as a power law when $c < c_q/3$, while, at finite frequency,
regions of negative excess noise are present due to Andreev-type resonances.
