### ASA 125th Meeting Ottawa 1993 May

## 4pSA8. Numerical predictions of acoustic radiation by unbaffled, finite
plates from non-intrusive velocity measurements.

**Todd L. Harbold
**

**
Courtney B. Burroughs
**

**
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*Appl. Res. Lab., Penn State Univ., P.O. Box 30, State College, PA 16801
*

*
*
The spatial distribution of the amplitude and phase of the velocity of
vibrating rectangular flat plates is measured using a scanning laser Doppler
vibrometer. These measurements are conducted in a nonanechoic environment with
the plate in air and water, driven by a single shaker at frequencies of
resonance and nonresonance. Using free-field Green's functions and fast Fourier
transform (FFT) algorithms, the free-field acoustic radiated field for the
unbaffled plate is determined. In order to compute the acoustic radiation, the
velocity field must be specified in the plane of the plate, both on and off the
surface of the plate. Therefore, an iterative process is used to determine the
velocity field off of the plate surface. Descriptions of the plate vibration
measurements and algorithms used to compute the free-field acoustic radiated
field are presented and discussed. Examples of results of measurements
conducted at and off resonance are given.