In sliding charge-density wave (CDW) conductors such as NbSe3, voltage oscillations at a frequency proportional to the local CDW velocity accompany CDW motion and can furnish many insights into the dynamics of these systems. We have used high-performance cryogenic differential amplifiers to make position-dependent measurements of voltage oscillations in the quasisteady state. These measurements yield voltage-voltage and velocity-velocity correlations and the temperature dependence of the CDW's longitudinal and transverse velocity coherence. © 2014 American Physical Society.