Analysis of Ambient Noise Spectrum Level Correlation Characteristics in the China Sea

Abstract

The ambient noise field in the ocean is formed by a mixture of many source types, such as seismic noise, marine noise, shipping noise, and wind-generated noise. The correlation matrices of the ambient noise spectrum levels offer a promising approach for identifying and isolating the active source mechanisms in ambient noise datasets. This study attempts to use frequency correlation matrices to examine inter-frequency relationships and identify frequency bands that are dominated by specific sources present in samples of ambient noise. Deep-ocean ambient noise recorded by hydroacoustic monitoring systems in the East China Sea and South China Sea was used to analyze the frequency correlation characteristics over a broadband frequency range, with a focus on the contribution of wind-related and shipping-related source mechanisms to the overall ambient noise field at various frequencies. The primary sources observed in both the South China Sea and East China Sea were shipping sources and wind sources. During the observation window, wind was responsible for a significant amount of the ambient noise energy above 477 Hz in the East China Sea, while the corresponding frequency threshold was shifted up to 575 Hz in the South China Sea. Another interesting feature was also observed in the East China Sea: a higher degree of correlation was found between the levels at the wind noise dominated frequencies and mixture noise (mainly consisting of wind noise and shipping noise) dominated frequencies at the upper receiver than at the lower receiver. Data analysis results show that the cause of this effect is that shipping activity contributes more to the soundscape at the lower receiver than at the upper receiver.

North Sea soundscapes from a fish perspective: Directional patterns in particle motion and masking potential from anthropogenic noise

“…Wave noise may also generate low-frequency sound up to 80 Hz, but wind-induced noise is typically gradually increasing in prominence toward 1 kHz and is most prominent between 1 and 10 kHz (Sertlek et al, 2019). The swell from distant storms can be highly directional (Wilson et al, 1985;Zhou, 2020) but would be expected to follow the main possible arrival trajectories from the north (northern parts of the North Sea) or southwest from the English Channel, which is again not reflecting the data.…”

“…B. Discarding some more alternative sound sources Distant shipping is a significant factor in many oceans and seas (Zhou, 2020), including the North Sea (Sertlek et al, 2019). The nearby Scheldt Estuary with the Western Scheldt serving Antwerp harbour and the Rhine Delta, serving Rotterdam harbour, would also make shipping noise a possible factor.…”

“…Arrays of multiple sound pressure sensing hydrophones have been used to model the directionality (beam forming) based on correlating the sensor position and variation in sound arrival times (e.g., Cox, 1973;Walker and Buckingham, 2012;Fried et al, 2013;Yang et al, 2018). Also, co-modulation at different frequency bands can be used to deduce spatial information through inference of the source directions and distances from the spectral coherence (Nichols and Sayer, 1977;Nichols and Bradley, 2019;Zhou, 2020). Vector sensors (Wilson et al, 1985;D'Spain et al, 2006;Thode et al, 2019) are probably one of the most informative methods and may match the perceptual world of fishes best (Popper and Fay, 2011;Nedelec et al, 2016;Popper and Hawkins, 2018).…”

Underwater Noise Characteristics of the Tidal Inlet of Zhanjiang Bay

“…The tidal pattern in Zhanjiang Bay is irregular and semidiurnal, with an average tidal range of about 2 m and a maximum tidal range of about 3.9 m. The total tidal volume is approximately 5 × 10 9 m 3 , with a maximum tidal volume of up to 10 × 10 9 m 3 . The tidal current velocity ranges from 0.5 to 1.5 m/s, making it an area with a relatively large tidal range along the coast of South China [22][23][24][25]. During high tides, the tidal current flows from the deep channel outside the bay into the bay; during low tides, the tidal current flows from the bay to the outside of the bay.…”

Machine Learning and Prediction of Masked Motors With Different Materials Based on Noise Analysis

“…In [13], a time-frequency graph was used to evaluate the noise suppression performance of a machine learning model. In [14] and [15], a time-frequency graph and correlation matrix were used to explore the influences of various noise sources around the South China Sea, such as ships, warships, plate movements, and wind, on the sound frequency ranges at sea [16]. The time-frequency diagram was used to compare the frequency-domain difference between an original signal and the same signal with various added noise signals.…”