Transducers of acoustic energy in a water medium have undergone a continuing evolution. Ferroelectric stacks have been used to drive piston or trains of ferroelectric elements have been used in long line arrays. Although there are a few exceptions, the ferroelectric elements seems to be more suited to operation in higher frequency ranges. Water hammers which sequentially interrupt the flow of an impelled fluid have been used by scientists when a low frequency sound source is called for. Somewhat better results have been obtained in the lower frequency spectrum, i.e. in the frequency band lying below 100 Hz, by using a magnetomotive motor driven transducer. One noteworthy design, "Transducer," disclosed in U.S. Pat. No. 3,126,520 by Frank R. Abbott, employed a magnetomotive diver motor over the mid-range of 100 Hz to several thousand Hz. The left and right hand pistons radiated this mid-range of acoustic energy by the magnetic interaction of AC and DC plates. Another design is the "Electrodynamic Transducer," of U.S. Pat. No. 3,353,040 also invented by the present invention, Frank R. Abbott. Stator and armature poles are mounted respectively on two concentric cylinders and bifilar windings are wound upon the two sets of poles. The sets of poles are excited by a DC signal and by an AC signal and the armature and interconnected piston face reciprocate at the same frequency as the applied AC signal. Still another electromechanical transducer called the "Electrodynamic Sonar Projector," U.S. Pat. No. 3,605,080 by Frank R. Abbott used magnetized ridges on an armature which is driven by a stator having interspursed AC and DC windings. In the frequency band below 100 Hz it functioned satisfactorily, yet this transducer, like its two predecessors, did not lend itself well to being towed through the water. Their bulk and lack of symmetry restricted their being used, for example, by scientists interested in mapping the marine topography by observing reflected signals over an extended area. Thus, there is a continuing need in the state-of-the-art to provide a high energy, low frequency transducer which is capable of being towed through the water while ensonifying the surroundings.
USPTO Backgrounds
USPTO Backgrounds