A low-frequency directional flextensional transducer and line array
- Naval Undersea Warfare Center, Newport, Rhode Island 02841 (United States)
- Image Acoustics, Incorporated, 97 Elm Street, Cohasset, Massachusetts 02025 (United States)
- Massa Products Corporation, 280 Lincoln Street, Hingham, Massachusetts 02043 (United States)
A unique low-frequency (900 Hz) class IV flextensional transducer that produces an 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 a thick-walled elliptical aluminum shell and a U.S. Navy type III piezoelectric stack along its major axis with two active sections and one inactive section. The directionality is achieved by simultaneously exciting the shell into an omnidirectional and dipole operation by driving stack into both extensional and bending modes. Both measurements and modeling on this device show a front to back pressure ratio of more than 30 dB, producing cardioid-type radiation patterns over an octave band, for a single transducer element. The transducers measured mechanical Q is 8, coupling coefficient is 0.25, and electroacoustic efficiency is 80{percent} and produced a source level of 215 dB {ital re:} 1 {mu}Pa at 1 m when driven at a field limit of 394 kV/m (10 kV/in.) at resonance. The uniqueness of this transducer is its directional beam patterns (directivity index=3.4 dB) and high acoustic output power from a small (less than a third of a wavelength) single element. Six of these transducers were placed in a closely packed line array two-wavelengths long. The array successfully produced narrow directional sound beams (directivity index=8.7 dB) with a front to back ratio greater than 30 dB and a source level of 225 dB {ital re:} 1 {mu}Pa at 1 m. {copyright} {ital 1997 Acoustical Society of America.}
- OSTI ID:
- 549297
- Journal Information:
- Journal of the Acoustical Society of America, Vol. 102, Issue 1; Other Information: PBD: Jul 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Development of a High Intensity Focused Ultrasound (HIFU) Hydrophone System
Threshold for Onset of Injury in Chinook Salmon from Exposure to Impulsive Pile Driving Sounds