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The directional response of a two‐ or three‐dimensional point array is a function of two independent directions and also a function of frequency. A suitable mapping of these three parameters into a pseudodirection and a pseudofrequency allows the examination of the major and minor lobe structure of the array response with only a two‐parameter computation. This method has been applied during the design of a 32‐element planar array, to permit adjustment of the element positions for a minimum and uniform minor‐lobe structure.

The directional‐response function of a linear array of uniformly spaced point sources is uniquely determined by the excitation coefficients of the array. The magnitude of the response function is a cosine series in the phase shift between signals from adjacent sources. In this paper, the converse problem—that of determining the excitation coefficients of an array so that the response of the array will be equal to a given cosine series—is examined. Not every cosine series can be realized as the response of an array, since the magnitude of the response function is nonnegative. Any nonnegative cosine series is factorable into a product of elementary cosine‐series factors, each of which corresponds to a 2‐ or 3‐element array. These simple arrays are then compounded into a multielement array having the specified response function. Although the response of the product array is not altered by a mirror‐image reversal of one of its factors, the excitation coefficients are changed. Thus, there can be several arrays having the same magnitude of directional response but having different excitation coefficients. Criteria for choosing among these equal‐but‐different arrays, such as phase response and spread of excitation coefficients, are examined.

Signals from a 110‐kHz side‐looking sonar have been digitally processed in real time to remove the variations due to small‐scale vehicle motions and transducer beam pattern. The residual signals can be used to measure the backscattering coefficient of the ocean bottom at grazing angles from 45° down to 6°. The system is calibrated by use of a cross‐frequency reference transponder. Data have been gathered in several areas of the Eastern Pacific and in the North Atlantic. [Work supported by U.S. Navy.]

A system for the analysis of acoustic signals from both transient and continuous sources has been developed for installation aboard the research platform FLIP. The system is built around a Digital Equipment Corporation PDP‐8/I computer. A six‐channel A:D converter allows simultaneous sampling of six hydrophone channels. The data are transmitted to core storage, and thence to an intermediate magnetic tape. The computer performs spectral analyses using the fast Fourier transform algorithm. Averaged spectrum values can be recorded on tape for later plotting, or displayed in real time on a cathode‐ray tube. [This report represents the results of research sponsored by the Office of Naval Research.]