### ASA 125th Meeting Ottawa 1993 May

## 2aEA6. Determination of electrical drives for a cylindrical wave-number
calibration array.

**L. D. Luker
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*Naval Res. Lab., Underwater Sound Reference Detachment, P.O. Box 568337,
Orlando, FL 32856-8337
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The ``flow noise'' produced by a turbulent boundary layer is generally
characterized by pressure distributions that are transported along the surface
at speeds much less than the sound speed in water and therefore have spatial
wave numbers that are larger than the acoustic wave number. This paper
describes several methods for computing the electrical drives for a prototype
cylindrical wave-number calibrator (CWC) designed to generate a pressure field
consisting of essentially a single nonacoustic wave number inside the
free-flooded calibrator. This geometry is suitable for the evaluation of line
acoustic sensors such as in towed sonar arrays. The prototype CWC consists of a
cylindrical tube of PVDF with an electrode pattern along the tube length that
allows the PVDF to be operated as 40 independent bands each of which can be
driven at a specified amplitude and phase. The required drive voltages are
calculated using the electroacoustic transfer matrix of the CWC at the desired
drive frequency. This transfer matrix can be determined by actual measurements
or by using a computer model of the CWC. Drives were computed using transfer
matrices that were determined with several modeling methods including the
acoustic-radiation program CHIEF and the finite-element program ATILA. Measured
pressure fields inside the CWC are compared with desired and predicted fields
at selected spatial wave numbers for drive frequencies of 800 and 1600 Hz.
These results are also compared with previous results produced using measured
transfer matrices. [Work jointly supported by ONR and ONT.]