A sound projector for acoustic tomography and global ocean monitoring
Citable URI
https://hdl.handle.net/1912/4298As published
https://doi.org/10.1109/JOE.2003.811888DOI
10.1109/JOE.2003.811888Abstract
Long-range underwater acoustic systems, such as
those used in ocean acoustic tomography, require low-frequency
signals covering a broad frequency band. To meet this requirement,
a novel design based on of a tunable narrow-band high-efficiency
sound projector has been exploited. The projector transmits a
frequency sweep signal by mechanically tuning a resonator tube
(or organ pipe) to match the frequency and phase of a reference
signal. The resonator tube projector consists of a symmetrical
pressure-balanced Tonpilz driver placed between two coaxially
mounted tubes. The Tonpilz acoustical driver is composed of two
pistons separated by preloaded ceramic stacks. The resonant tube
is a simple. efficient, narrow-band, medium-output projector that
operates at any ocean depth. Both projector tubes have slots (or
vents), which are progressively covered or uncovered by sliding
coaxial tubular sleeves. The frequency varies with the sleeves
position. A computer-controlled electromechanical actuator moves
the cylindrical sleeves along the tubes, keeping the projector in
resonance at the instantaneous frequency of a swept frequency
signal. The actuator smoothly tunes the frequency of the resonator
tube in the bandwidth of 200 to 300 Hz during a 135-s transmission.
A computer synthesizes the linear frequency-modulated signal;
compares the phase between transmitted and reference signals;
and, using a phase-lock loop (PLL) system, keeps the resonator
tube frequency in resonance with the driver frequency. The
estimated PLL precision is better than 3 phase error. The system
was analyzed by means of finite element analysis and electrical
equivalent circuit simulation. The projector prototype was first
tested at theWoods Hole Oceanographic Institution (WHOI) dock
inWoods Hole, MA and later in the Pacific Ocean during a voyage
of the R/V “Point Sur,” November 2001.
Description
Author Posting. © IEEE, 2003. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in IEEE Journal of Oceanic Engineering 28 (2003): 174-185, doi:10.1109/JOE.2003.811888.
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IEEE Journal of Oceanic Engineering 28 (2003): 174-185Related items
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