Phase II year
2017
(last award dollars: 2023)
Phase II Amount
$2,516,481
Systems that operate in constrained environments depend on the acoustics in several ways. Harbor defense systems detect intruders (people and/or vessels) by either listening for their noises (passively) or by pinging on them and detecting their echoes (actively). Furthermore, such systems may also form the equivalent of an underwater cell phone network using sound to carry the information. The acoustic channel may be used to control the underwater system or to provide information back to a shore-based site. For instance, the RFP mentions a Phase III transition to the Advanced Undersea Weapons System in which mines are controlled through an acoustic comms network. Acoustic models allow one to predict system performance and then optimize system parameters, such as the location of sonar transmitters and receivers. This project will lead to mature propagation and reverberation models for that application.
Benefit: This work will leave to a mature model and tactical decision aid for use in constrained environments. The primary beneficiary will be the U.S. Navy with practical security concerns for harbors. The resulting package will also be useful for civilian applications related to port security and for a variety of applications involving acoustic communication networks.
Keywords: Harbor, UUV Detection, communications performance, Three-Dimensional, Acoustics ---------- The goal of this work is to demonstrate and validate a 3D acoustic propagation model for use in constrained environments such as harbors. The 3D model will be used to model system performance for 1) passive sonar, 2) active sonar, and 3) acoustic communications networks. This latter application is of primary importance in this Phase II Extended proposal. To accomplish these goals are sequence of field tests has been proposed in diverse sites including harbors and estuaries. In these field tests a variety of measurements will be made. The environment, especially bathymetry will be measured using specialized autonomous systems called Jetyaks. The ocean propagation conditions will also be measured using the Jetyaks as receivers to record the echo pattern in the channel due to a towed source. Finally, the Woods Hole acoustic communications group will measure modem performance in these same conditions. By analyzing all this data we hope to demonstrate a reliable predictive capability for modem performance in such constrained environments. This in turn will enable modem networks to be optimized for other constrained environments in terms of network geometry as well as modem parameters such as data rate and modulation scheme.
Benefit: As mentioned in the Technical Abstract, there are a variety of Navy systems that operate in constrained spaces such as harbors. To mention just a few, both passive (listening only) and active (listening to transmitted pings) sonar systems are important in ensuring harbor security. In a mostly distinct area, acoustic modems are often key in networking a variety of fixed and mobile platforms in harbors. Much is know about acoustic modem performance in deeper areas. However, harbors and other constrained environments are very different in terms of complicated reflections off features such as seawalls, docks, piers, and ship hulls to name just a few examples. These features of constrained environments are very different to what one finds in the open ocean where sound propagation is generally assumed to be confined to radials from the source. Further, these features produced complicated echo patters that are believed to degrade the modem performance. This work will significantly enhance the modeling capability. Besides the Navy systems that operate in such environments, commercial acoustic modems are also used for a variety of similar applications so there is significant value for both Navy and commercial applications.
Keywords: Modem, Harbors, Sound, constrained spaces, Acoustics
