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Results from two parametric nearfield experiments have been reported. The data, known to contain substantial receiving hydrophone intermodulation distortion, have been corrected to deducing the level of the distortion and coherently subtracting the distortion pressure from the measured data. A test of several nearfield theories has been made. Because of the condition of the experimental data, the test is not particularly discriminating. Also, there is not a great deal of spread among the theories considered.

The report describes an investigation concerning parametric sonar applications to under-ice operations. Two basic tasks are undertaken. These are first, a data gathering program in an environment which partially simualtes the under-ice environment; and second, a theoretical investigation which extrapolates the results obtained to the under-ice environment. To gather data in a representative environment, a parametric sonar operating in a sub-bottom profiling mode was used in a downward looking mode analogous to upward scanning of the water to sea-ice interface. Results were analyzed and compared to possible under-ice operations in the theoretical investigations.

Finite Amplitude Sonar, also referred to as Parametric or Non-Linear Sonar, requires generation of high acoustic source levels. These high levels require high electrical powers and may stress transmitter and transducer components beyond normal linear ranges. Unless guarded against, such stresses introduce distortions into the signal paths and degrade the unique properties of Finite Amplitude operation. This report describes various transducer and transmitter configurations which can be applied to Finite Amplitude Sonar and discusses the potential advantages and disadvantages of each. Two opposing requirements are considered--high source levels and minimum signal distortion.

The manual contains descriptions and schematics of the proportional bandwidth spectrum analyzer (PBSA). It contains a brief description of the overall system, more detailed functional descriptions of the parts of the system, and schematics with timing diagrams and magnetic core layouts. The manual is divided along these lines into the three parts: General information; theory of operation; and, schematics. The PBSA is a signal processing portion of a developmental device to be used for research in underwater acoustic reception.