  We compute exactly the non-equilibrium DC noise in a Luttinger liquid with an
impurity and an applied voltage. By generalizing Landauer transport theory for
Fermi liquids to interacting, integrable systems, we relate this noise to the
density fluctuations of quasiparticles. We then show how to compute these
fluctuations using the Bethe ansatz. The non-trivial density correlations from
the interactions result in a substantial part of the non-equilibrium noise. The
final result for the noise is a scaling function of the voltage, temperature
and impurity coupling. It may eventually be observable in tunneling between
edges of a fractional quantum Hall effect device.
