Empirical ambient noise model based on wind speed using two-decade open ocean ambient noise data in the frequency band of 1–20 kHz

In the frequency band of 1–20 kHz, wind-generated breaking surface waves produce bubbles near the surface that are the dominant ambient noise source. In previous work, two decades of ambient noise data from six deep ocean moorings were used to validate ambient noise models (Yang et al., JASA EL 3(3), 2023). Data-model comparisons show a mismatch, as existing models are monotonic in nature, i.e., the modeled spectral level increases with increasing wind speed for all frequencies, while data display a sharp drop-off that creates a “cross-over” as the spectral level for wind speed exceeding 15 m/s and frequency above ∼4 kHz becomes lower than that at lower wind speeds. This mismatch is due to attenuation when ambient sound propagates through the deeper and denser bubble layer under high sea conditions. In this work, an empirical ambient noise model utilizing wind speed only is presented as a baseline prediction with potential fine-tuning parameters such as bubble statistics, current and its direction, and wave height discussed. Work supported by NOAA, NASA, and ONR.