Ocean acoustic waveguide invariant parameter estimation using tonal noise sources

The abundance of shipping noise sources in ocean littoral zones provides a great opportunity to estimate ocean environmental parameters. The waveguide invariant parameter β, defined as the ratio of inverse group and phase velocities between modes, has been used in a variety of applications including ranging of passive sources. Previous work utilizing the waveguide invariant in passive sonar has relied on processing the time-frequency intensity striations of broadband sources. In this paper, the reception of strong tonal components from transiting commercial ships of known location (e.g., from AIS data) are used for estimating β over the source-receiver path. A maximum likelihood estimate of β is derived by relating the fading characteristics of different tonal components over range. The method is verified on simulated data using a Pekeris waveguide model.