2023_programme: Modeling Low Frequency Wind-Generated Noise

• Session: 03. Comprehensive Nuclear-Test-Ban Treaty Monitoring and its Civil and Scientific Applications
  Organiser(s): Georgios Haralabus, Mario Zampolli and Peter Nielsen
• Lecture: Modeling Low Frequency Wind-Generated Noise [invited]
  Paper ID: 1910
  Author(s): Stockinger Christopher, Wilson Preston, Hartman John
  Presenter: Stockinger Christopher
  Abstract: Historically, shipping is assumed to dominate ambient underwater acoustic Noise Levels (NL) from 10 to 100 Hz, however, the data acquired from the north hydrophone triplet of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) station at Crozet Island provides unique wind noise observations with minimal shipping interference. First, NL was correlated to local wind speed through a frequency dependent power relation, and second, the distant wind contributions were modeled through a source density and propagation model. For the source density model, wind-related noise was modeled as a layer of monopole sources located at a quarter wavelength below the surface to replicate a dipole radiation pattern. The total acoustic intensity received by the array and the modeled wind-related source intensity were both related to wind speed through a power relationship where the two share the same frequency dependent exponent, n. The two coefficients and the exponent were computed empirically from the acoustic and wind speed data. An important observation is that the exponent n increases as frequency decreases and reaches a value n > 7 at 10 Hz, which is much larger than the n = 3.5 often measured at 300 Hz (the frequency regime of peak wind-dependent bubble and spray noise). The source layer model accurately predicts the NL within a standard deviation of 3 dB and is necessary with low local wind speeds. The model was utilized to determine that sources over 1600 km away influence the NL measurement at these frequencies.
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• Corresponding author: Mr Christopher Stockinger
  Affiliation: The University of Texas at Austin
  Country: United States
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