Linear chain compounds exhibiting CDW transport have CDW wavelengths λ cdw = π/k F incommensurate with (i.e., not an integer multiple of) the lattice constant. In such materials, pinning is due to impurities that break the translational symmetry of the CDW with respect to φ. The simplest model treats the pinning as a sine-Gordon potential of the form u (φ) = u 0 [1 – cos φ ], while the electric field tilts the periodic pinning potential until the phase can slide over the barrier above the classical depinning field. Known as the overdamped oscillator model, since it also models the damped CDW response to oscillatory (AC) electric fields, this picture accounts for the scaling of the narrow-band noise with CDW current above threshold.