The general practice of acoustic leak location relies on two different physical phenomena for determining source location: 1) reduction in signal amplitude with increasing distance from the source (attenuation-based methods), and 2) increase in signal transit time with increasing distance from the source (time-of-flight-based methods). The work discussed here describes efforts at ISU directed at gaining first-principle understanding of the underlying physical phenomena of multi-mode dispersion in fluid filled pipes and to developing time-of-flight source location data processing for such dispersive systems. Results are presented for work detailing the characteristics of pipe propagation, as well as the effect of those characteristics on cross-correlation analysis. Theoretical and experimental results are also shown for two approaches which potentially overcome the limitations of cross-correlation techniques.