3pSP10. A low-frequency directional flextensional transducer and line array.

Session: Wednesday Afternoon, December 4

Time: 4:35

Author: Stephen C. Butler
Location: Naval Undersea Warfare Ctr., New London, CT 06320
Author: John L. Butler
Location: Image Acoust., Inc., Cohasset, MA 02025
Author: Alexander L. Butler
Location: Image Acoust., Inc., Cohasset, MA 02025
Author: George H. Cavanagh
Location: Massa Products Corp., Hingham, MA 02043


A unique low-frequency (900 Hz) Class IV flextensional transducer which produces enhanced far-field pressure on one side and canceled far-field pressure on the other side has been developed. The transducer radiating surface consists of an elliptical aluminum shell and a piezoelectric stack along its major axis with two active sections and one inactive section. The directionality is achieved by exciting the shell into an omnidirectional and dipole operation by driving the ceramic stack into both extensional and bending modes. Both measurements and modeling on this device show a front to back pressure ratio of more than 25 dB, producing cardioid type radiation patterns over an octave band. The measured mechanical Q, coupling coefficient, and electroacoustic efficiency were found to be approximately 8%, 0.25%, and 80%, respectively, and the transducer produced a source level of 215 dB re: 1 (mu)Pa/m. Six of these transducers were placed in a closely packed line array. The array successfully produced narrow directional sound beams with a front to back ratio greater than 25 dB and a source level of 225 dB re: 1 (mu)Pa/m. [Work supported, in part, through a U. S. Navy SBIR contract.]

ASA 132nd meeting - Hawaii, December 1996