M. K. Beason
L. D. Luker
Underwater Sound Reference Detachment, Naval Res. Lab., P.O. Box 568337, Orlando, FL 32856-8337
This presentation considers the effect of projector design on reducing pressure-field deviations within the long-line hydrophone calibrator (LLHC). The LLHC is a water-filled traveling-wave tube which simulates a plane-wave pressure field arriving from any bearing. This is accomplished by measuring the electroacoustic transfer matrix between hydrophones and projectors that are placed within a steel pipe with an inner diameter of approximately 30 cm. This transfer matrix is then used to compute projector drives suitable for creating the desired field. Two types of projectors were investigated for use in the LLHC: (1) single-element projectors using a hollow PZT-4 sphere with an outer diameter of 38.1 mm and a wall thickness of 4.76 mm, and (2) projector lines constructed of 10 capped cylinders of PZT-4 with 12.7 mm length, 12.7 mm diameter, and 0.79 mm wall thickness. Model simulations and measured data will be presented indicating that the extended-source projectors result in lower deviations from the desired pressure field than single-element projectors at the same spacing. [Work supported by NAVSEA.]