Abstract: A method is disclosed for calibration of a towed line array. In a low frequency band, calibration is performed using an acoustic field observed by reference standard hydrophones. The observations form a model of a complex acoustic field throughout a space occupied by a measurement apparatus. The array sensitivities are computed by comparing output voltages of the array with the acoustic field estimated at the locations occupied by hydrophones of the array. Variations in the acoustic field that cannot be accounted for by free field propagation theory are included in the calculation of array channel sensitivities. The method extends the low frequency limit for the calibration to less than the minimum frequency at which free field propagation conditions can be approximated. Boundary reflections and spatial variations in the acoustic field are recognized. The spatial distribution of acoustic energy is used to provide low frequency calibration with improved precision.

Abstract: A method is disclosed for calibration of a towed line array. In a low frequency band, calibration is performed using an acoustic field observed by reference standard hydrophones. The observations form a model of a complex acoustic field throughout a space occupied by a measurement apparatus. The array sensitivities are computed by comparing output voltages of the array with the acoustic field estimated at the locations occupied by hydrophones of the array. Variations in the acoustic field that cannot be accounted for by free field propagation theory are included in the calculation of array channel sensitivities. The method extends the low frequency limit for the calibration to less than the minimum frequency at which free field propagation conditions can be approximated. Boundary reflections and spatial variations in the acoustic field are recognized. The spatial distribution of acoustic energy is used to provide low frequency calibration with improved precision.