Abstract: A system is presented for enhancing sonar signals wherein Doppler echoes eived in the time domain from a sonar system are processed by digitizing, shifting to baseband, Fourier transforming to the frequency domain, applying a frequency stretching algorithm designed to expand low Doppler signals, retransforming the signal back to the time domain, reshifting from baseband to original center frequency, converting to analog and outputting the resultant enhanced Doppler time domain signals to either earphones of a sonar operator for audio monitoring or for further processing for visual display.

Abstract: A system locates the elements of a randomly dispersed, untethered, array of sonobuoys from which are suspended active, transmitting, transducer elets and passive, receiving, transducer elements. The system comprises a data conditioning unit which receives high-frequency element-locating signals from a radio receiver, which may be located on an aircraft, and processes them so that they are quantized at its output. An acoustic delay processor, whose input is connected to the output of the data conditioning unit, correlates a reference signal R received from an active element suspended from the sonobuoy with a corresponding received signal from another element, active or passive, suspended from another sonobuoy.A position tracker, whose input is connnected to the output of the acoustic delay processor, calculates the relative position of each element of the random array from the propagation delays measured by the acoustic delay processor.

Abstract: A Frequency Dispersive Transmitting Array (30) for propagating composite e energy (10) emulates narrow-band beams (20) of different frequencies which can be simultaneously radiated in all directions, or in any subset of directions, relative to an array (42) of radiating elements (32) because of the addition and cancellation of components of wave energy (10) radiated, is disclosed. A signal source (34) provides input signals (36), having frequencies which may be acoustic or electromagnetic, which are coupled by feedline (37) to radiating elements (32) through a plurality of time delay devices (38). Each one of time delay devices (38) is interposed between successive ones of radiating elements (32) and delays emission of replicas of signals (36) therefrom by a time delay .tau..sub.0 which is a multiple of the period of the dominant frequency radiated in a direction broadside to the array.

Abstract: An air deployable, volumetric hydrophone array uses three horizontal booms adiating from a central hub suspended at the array operating depth. Loose lines of hydrophones are hung from pairs of points on the boom structure and hang in arcs approximating catenaries.

Abstract: An acoustic, underwater, telemetry system between two vehicles, a free-rung, deep-operating, sonar platform, or Sonaray vehicle, to overcome refraction, and a surface ship to provide processing of the sonar data gathered by the Sonaray vehicle. The telemetry system is required to communicate analog sonar information, digital command to control the platform, and digital information concerning the status of the platform, between the Sonaray vehicle and the surface ship. The Sonaray concept requires more than 32 channels of analog information for sonar data transmission, each corresponding to a particular received azimuthal beam and each having an information bandwidth of 1 kHz. The output of the analog channels consists of raw data from the search sonar. Because of the long range and very high reliability of the transmission required for the status and control channels, sonar processing by cross-correlation is used to search in both range and doppler.

Abstract: A transducer assembly comprising: a diaphragm; at least one transducer elnt bonded by its head to the diaphragm; a pressure-resistant means, for supporting the transducer assembly; an acoustic isolator mounted about the transducer element and located between the diaphragm and the pressure-resistant means; the material of the acoustic isolator being elastically linear and equal in thickness to one-quarter wavelength of the corresponding operating frequency of the transducer element.