300 Hz and 500 Hz Autonomous Acoustic Sources


FLC Region

Security Lab



Chesapeake Beach


FUNCTION: Provide acoustic researchers with autonomous, bottom-moored sound sources, which provide precise, highly stable frequency transmissions at GPS trackable times. The accuracy of the sources enables research into environmental perturbations of sound propagated through ocean media.

DESCRIPTION: The equipment consists of two sources, one centered at 300 Hz and another at 500 Hz. Each source uses a pressure-compensated flexural bar projector. The sources have a bandwidth of +/-10% about the center frequency. The accuracy of the transmit time and transmit frequency is controlled by a rubidium oscillator that can be disciplined to the GPS satellite system before deployment. The output level is adjustable with a maximum output of 183 dB. Pucks of D-cells contained in two pressure housings provide energy. The systems are rated to 200 meters. A full complement of pucks allows the sources to operate for 21 days at a 50% duty cycle and output level of 181 dB. Each system has an internal rubidium oscillator, and PC-104 electronics for timing and frequency generation. The systems are capable of continuous-wave, frequency modulated (FM) waveforms and arbitrary pseudorandom waveforms. Waveform types can be mixed within a transmit schedule, being limited only by the projectors, available programmable system memory, and energy levels desired.

INSTRUMENTATION: There are two independent systems. Each system consists of an EAI projector, Seascan signal generator/system, PC-104 electronics, and Webb Research assembly. One operates at 300 Hz and the other at 500 Hz. Each system includes a pressure-compensated projector, two pressure housings, and internal programmable electronics for transmit frequency and waveform, plus timing control.


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