The auditory system can extract temporal information from complex stimuli to perform a variety of detection and discrimination tasks. At low stimulus frequencies, the auditory system may encode stimulus fine structure and temporal envelope. At higher frequencies, the coding of fine structure diminishes as phase locking deteriorates, while the coding of the temporal envelope remains. The present study investigated the relative contributions of interaural differences in stimulus envelope and fine structure to the masking level difference (MLD). NoSo and NoS thresholds were measured at stimulus frequencies of 500 and 4000 Hz using two types of narrow-band (50 Hz) noise: Gaussian and low-noise noise. Gaussian noise maskers yielded MLDs of 15 at 500 Hz and 9 dB at 4000 Hz, the reduction reflecting minimal fine structure cues at 4000 Hz. Low-noise noise yielded lower NoSo and higher NoS thresholds than Gaussian noise. MLDs of 8 at 500 Hz and 0 dB at 4000 Hz reflected minimal masker envelope cues in both conditions and reduced fine structure cues at 4000 Hz. While the pattern of results was consistent, threshold differences among the six listeners were substantial. Additional MLD conditions and data from CMR and noise discrimination tasks employing low-noise noise will be discussed.