  We have investigated nonlinear characteristics and broad band noise in the
quasi-one dimensional charge-density-wave conductors K0.30MoO3 and
K0.30Mo(1-x)WxO3 (x=0.001 and x=0.002) When the amplitude of a bipolar
rectangular voltage pulse excitation is modulated by adding a white noise
perturbation, the average pulse amplitude is smaller than the unperturbed one
and shows a non monotonous behaviour when the pulse amplitude is increased. Our
findings suggest that coupling between internal broad band noise and external
white noise may lead to an increase of phase coherence of the
charge-density-wave.
