LOW-FREQUENCY VOLUME REVERBERATION MEASUREMENTS

An experimental technique has been developed to measure broadband low-frequency volume reverberation. Experiments were performed in the North Atlantic with broadband explosive sources in conjunction with the end-fire beam of a vertical line array to provide scattering strength contours from measurements sampled in both frequency (approximately 12 Hz) and depth (approximately 4 m). The average effective resolution in frequency (approximately 100 Hz) and depth (approximately 30 m) resulted from signal processing procedures and geometrical effects associated with the measurements. During the measurements a SIMRAD scientific echo sounder system was utilized. This system incorporates split-beam processing technology to provide the most accurate in-situ assessment, analysis, and display of biological target strength. and fish length distributions. The experimental and analysis techniques are described along with representative examples that compare high and low scattering levels observed during the experiment.