Measured and modeled high-frequency acoustic impulse responses in very shallow water

A goal of the Center for Island, Maritime, and Extreme Environment Security (CIMES) is to develop passive acoustic methods to monitor harbor and near-shore environments. Advantages of passive systems include source classification capabilities (since sound sources have different signatures), improved detection and tracking capabilities in cases when sonar avoidance and jamming technologies are used, the ability to monitor the environment without alerting the intruder, and minimal environmental impact for sensitive areas. Localization and tracking of targets relies on understanding the acoustic field properties and propagation characteristics. For this reason, a series of experiments were conducted to determine empirical impulse responses and to evaluate the performance of acoustic propagation models at high-frequencies (10-80kHz). The experiments were conducted on site of the CIMES passive acoustic system, which is near-shore in shallow (~10m) water off the south shore of Oahu, Hawaii. This paper presents the methods and results of these experiments and compares them with acoustic propagation model predictions. Implications for passive acoustic tracking are discussed.