Analysis of impulsive biological noise due to snapping shrimp as a point process in time

Impulsive biological noise produced by snapping shrimp provides an important contribution to the ambient acoustic noise in warm, coastal waters. The challenge is to understand and model the properties of shrimp noise to reduce its impact on sonar and underwater acoustic telemetry systems. Shrimp snaps are impulsive events occurring apparently at random. The short duration of each snap allows these events to be modeled as a point process in time. Point processes are used to model many naturally occurring phenomena including neuron firings, seismic events, radioactive decay, lightning discharges and shot noise in semiconductors. In this paper, point process analysis techniques are applied to real shrimp noise. Inter-snap interval histogram and Fano-factor analysis provide strong evidence that the snaps are not homogeneous Poisson distributed in time. Further analysis based on the rate function suggests that the data may be more appropriately modeled by a doubly stochastic Poisson process.