Array Performance: A Methodology of System Calibration and Noise Identification.

摘要

The assumption that acoustic array measurements are a true reflection of the oceanic noise field can lead to misinterpretation of the data collected. Characterization of the array self noise levels and knowledge of individual element amplitude and phase responses are required to assess the results with confidence. In recent years emphasis on low frequencies and high resolution has led to the development of large aperture arrays with many elements. Establishing individual element calibrations and system noise levels of these arrays is not easily achieved in the laboratory environment due to facility and time constraints. Therefore, a series of tests are suggested to assist in the identification of system noise sources in such an array using a combination of oceanic ambient noise measurements and limited laboratory measurements. An in-situ element calibration is also discussed which compares magnitude estimates from two independent methods and generates a phase error curve. These methods are somewhat limited by incomplete knowledge of the environmental parameters and the statistical nature of ambient noise. Results are demonstrated using data collected by a large aperture vertical array deployed from the research platform Floating Instrument Platform (FLIP) in the Northeast Pacific. Acoustic arrays; Oceanic ambient noise; System noise sources; Electronic equipment; Flip. (jg)