New Models on the Ocean Acoustic Detection Process

Abstract

The basic problem of the ocean acoustic detection process is formulated analytically under the assumption of fully developed saturated phase random multipath acoustic fluctuations. Detection is defined as occurring whenever ρ, the root‐mean‐square pressure at the receiver, exceeds a specified threshold level ρ0. Two models, one exact and one approximate, are developed for obtaining the probability density functions of the time between two successive detections and of the time ρ is above ρ0 (holding time). The two models are compared with one another and with the extensively used (λ, σ) model. One of the reasons that the latter model has a limited success in practice is the inability to estimate the appropriate value for λ, a parameter which is determined empirically. In this paper we have derived an appropriate value for λ, in terms of ν (the single path root‐mean‐square phase rate), σ21 (half the long time average mean‐square pressure at the receiver) and ρ0 (the threshold level). Using this equivalent value for λ, we observe that our exact and approximate detection models exhibit similar long‐term behavior but markedly different short‐term characteristics as compared with the (λ,σ) model. This is due to the memory of the process, a property that cannot be accounted for in the (λ,σ) model. A comparison of these models with data obtained from various field experiments demonstrates, in most cases, an improved capability over the (λ,σ) model.