Optimal beamforming on synthetic noise and interference is a flexible and intuitive technique for shaping beam patterns. In this method, suppression of arrivals from undesirable directions is achieved through introduction of synthetic interferences and optimal beamforming using the resulting noise-interference covariance matrix. We apply this approach to a general multiplet line array and test the algorithm on representative multi-channel time-series obtained for a quadruplet line array.

Computer systems for generating simulated underwater sound have been in use for more than 30 years. Such systems, including the author%u2019s sonar simulation toolset (SST), enable users to build an artificial ocean that sounds like a real ocean, as heard by a user-specified listening system. Such signals are useful for designing new acoustic systems for undersea sensing or communication, testing existing systems, predicting performance, developing tactics, training operators, planning experiments, and interpreting measurements. Signals of interest include reverberation, target echoes, discrete sound sources, and background noise. The author will describe, in broad outline, techniques for generating simulated underwater sound and criteria for choosing among them, focusing on target echoes and reverberation for active sonar systems. The characteristics of the ocean as an acoustic medium, the characteristics of the sensors, the processing and display systems behind the sensors, the purpose of the simulation, and the computational resources available for the simulation all strongly influence the choice of algorithms to achieve useful, cost-effective, simulated underwater sound. The characteristics of the human auditory system are of minor importance.

The Sonar Simulation Toolset (SST) is a computer program that produces simulated sonar signals, enabling users to build an artificial ocean that sounds like a real ocean. Such signals are useful for designing new sonar systems, testing existing sonars, predicting performance, developing tactics, training operators and officers, planning experiments, and interpreting measurements. SST's simulated signals include reverberation, target echoes, discrete sound sources, and background noise with specified spectra. Externally generated or measured signals can be added to the output signal or used as transmissions. Eigenrays from the Generic Sonar Model (GSM) or the Comprehensive Acoustic System Simulation (CASS) can be used, making all of GSM's propagation models and CASS's Gaussian Ray Bundle (GRAB) propagation model available to the SST user. A command language controls a large collection of component models describing the ocean, sonars, noise sources, targets, and signals. The software runs on several UNIX computers, Windows, and Macintosh OS X. SST's primary documentation is the SST Web (a large HTML "web site" distributed with the SST software), supported by a collection of documented examples.

This report emphasizes the science, mathematics, and algorithms underlying SST. It is intended to be updated often and distributed with each release of SST as an integral part of the SST documentation.