  We calculate the power spectrum of electric-field-driven ion transport
through cylindrical nanometer-scale pores using both linearized mean-field
theory and Langevin dynamics simulations. With the atom-sized cutoff radius as
the only fitting parameter, the linearized mean-field theory accurately
captures the dependence of the simulated power spectral density on the pore
radius and the applied electric field. Remarkably, the linearized mean-field
theory predicts a plateau in the power spectral density at low frequency
${\omega}$, which is confirmed by the Langevin dynamics simulations at low ion
concentration. At high ion concentration, however, the power spectral density
follows a power law that is reminiscent of the $1/{\omega}^{\alpha}$ dependence
found experimentally at low frequency. Based on simulations with and without
ion-ion interactions, we attribute the low-frequency power law dependence to
ion-ion correlations. Finally, we show that the surface charge density has no
effect on the frequency dependence of the power spectrum.
