Calculating the source directivity index for developing hydrophones

When designing new acoustic transmitters, an important feature is the source directivity index. Source directivity is often computed using measurements obtained within a water tank environment. The goal of this work is to determine the frequency range over which the water tank in the Underwater Acoustics Lab at Brigham Young University is a suitable environment to determine the directivity index of an acoustic transmitter. A source transducer with a known directivity index is introduced into the tank environment. A receiver with known sensitivities records linear chirps and pulses along a spherical arc. The pulses are timegated based on their position within the tank environment and analyzed in the frequency domain. Overall sound pressure levels are compared with the one-third-octave band levels, and the directivity index is computed. After verifying its feasibility, the procedure is repeated with different transmitters. This work will prepare the tank environment for future studies pertaining to source directivity. [Undergraduate Research supported by the College of Computational, Mathematical, and Physical Sciences at Brigham Young University.]