An all-atom molecular dynamics (MD) simulation of dilute HDO in H2O was used to obtain vibrational frequency spectra from the classical MD trajectories and a wavelet-based method was developed to obtain the frequency-frequency correlation functions (FFCFs) of the OD stretch vibrations. Time constants were obtained on the order of 30 fs, 150–260 fs and 3.2–3.6 ps. An OD covalent bond length correlation function was calculated and a long-timescale decay constant of 1.73 ps was obtained, similar to experimental values that range from 1.45 ps to 1.8 ps. An O-O hydrogen bond length correlation function was calculated and found to exhibit an oscillation at 150 fs and a long-timescale decay time of 3.47 ps, both in good agreement with the FFCFs. Such results suggest that the spectral diffusion observed in FFCFs can be primarily attributed to fluctuations in O-O distances. An OD stretch energy correlation function was calculated, which consists of exponential decay with a time constant of 1.13 ps. The energy correlation function also exhibits two oscillations that are indicative of resonant energy transfer processes involving the OD stretch.