Passive Acoustic Thermometry Using Low-Frequency Deep Water Noise

Abstract

Abstract : The long-term goal is to develop a passive modality of acoustic thermometry using Cross-correlation processing of deep water ambient noise. Our previous research effort has demonstrated that coherent processing of shipping noise (100HzfkHz) in shallow water can provide a totally passive means for sensing the ocean environment; but optimizing this correlation process for this relatively high frequency band remains challenging in a fluctuating ocean environment with significant multipath. We hypothesize that using instead significantly lower frequency (f50Hz) ocean noise recorded in the SOFAR channel may enhance the performance of this correlation process due to the potential long-range spatial correlations (100kms) of this deep water noise field and the relative temporal stability of the SOFAR channel. The main objective of this year research was to assess the feasibility of passive (i.e. noise-based) acoustic thermometry using low-frequency deep water ambient noise recorded on the global IMSCTBTO network Results from this study are expected to help guide the design of future cabled or autonomous ocean observatory systems for passive ocean monitoring.