In-situ non-acoustic noise measurement system for towed hydrophone array

Frequency wave number analysis is a standard tool to separate acoustic and non-acoustic noise in underwater towed array sonar. In order to measure absolute levels of the noise components, the paper proposes introduction of a reference acoustic signal source for the in-situ noise level measurement system based on this principle, It also introduces ALE preprocessing followed by f-κ analysis on its outputs. The measurement system was evaluated on Digital Thin Line Array(DTLA). The approach can be extended to the case, where the reference signal frequency is unknown and also it is continuously drifting. In such cases, the automatic frequency identification and tracking method suggested in [8], [9] can be used to estimate the signal power P_s and the ratio r₂. This method is useful, especially when own ship emanated tonal is used as the reference.