2019_programme: SURFACE GENERATED NOISE IN A FRESHWATER RESERVOIR



  • Session: 06. Underwater Noise - Modelling and Measurements
    Organiser(s): Gavrilov Alexander, Skarsoulis Emmanuel, Taroudakis Michael
  • Lecture: SURFACE GENERATED NOISE IN A FRESHWATER RESERVOIR [invited]
    Paper ID: 1008
    Author(s): Cato Douglas
    Presenter: Cato Douglas
    Presentation type: oral
    Abstract: Measurements of ambient noise in Woronora Dam, a freshwater reservoir south of Sydney, Australia, showed that noise from the water surface followed similar trends to those observed from the sea surface in the open ocean, but with some interesting differences. Recordings were made with an autonomous moored system in 35 m water depth over the frequency range 0.33 Hz to 24 kHz (-3 dB points). Wind speed was recorded from an anemometer on a mast on a moored pontoon about 100 m from the hydrophone. Wave height measurements were measured with a capacitive wave staff. Initial measurements showed particularly low noise levels, so further measurement were made with a very low noise, high impedance preamplifier at the hydrophone output to obtain significantly lower electronic noise than is usually used in underwater recording systems. The lowest measured noise levels were well below those usually measured at sea. Very low frequency noise cause by a non-linear effect of surface wave interaction peaked at higher frequencies than at sea, consistent with the higher frequency peak in the surface wave spectrum. Noise from breaking waves at frequencies above 100 Hz showed a similar dependence on wind speed as observed at sea for locally measured wind speeds, but levels were much lower for the same wind speeds and did not show the low frequency (below a few hundred hertz) component evident at sea.
  • Corresponding author: Prof Cato Douglas
    Affiliation: Defence Science & Technology Group and University of Sydney
    Country: Australia
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