The Shallow Water 2006 (SW06) experiment was conducted in the Mid-Atlantic continental shelf off the New Jersey coast. A fast-sampling, 48-channel hydrophone array system recorded a number of sei whale (Balaenoptera borealis) vocalizations during this time. This system had 16 hydrophones on the vertical line array (VLA) component covering the water column from 13-m depth to the bottom (80 m) and 32 hydrophones on the 480-m horizontal line array (HLA) component that lay on the bottom. The sei whale receptions on the arrays are low-frequency (less then 100 Hz) downsweep chirps and have the typical acoustic modal arrival pattern seen in shallow-water, low-frequency sound propagation. Due to acoustic modal dispersion, the frequency sweep durations observed from the receptions are found to be longer than the original signal. A horizontal beamforming technique using the HLA component is implemented to determine the bearings to whales. The whale location along the determined bearing and the frequency sweep rate of original whale sound are simultaneously estimated using the VLA component with a multiple-parameter optimization technique. This optimization technique is based on acoustic normal mode theory and is designed to compensate for the effect of acoustic modal dispersion.