Depth Spatial Characterization of Marine Environmental Noise in the Zengmu Basin

Abstract

Based on the measured data obtained from an array of optical fiber hydrophones, this paper analyzes and interprets the depth spatial spectrum characteristics, correlation characteristics, and vertical directionality of marine environmental noise in the Zengmu Basin. The analysis is conducted within the frequency range of 20 Hz to 2500 Hz. Additionally, the statistical characteristics of the probability density distribution of environmental noise in the Zengmu Basin were studied and analyzed. The findings indicate that the predominant ambient noise in the low-frequency range (less than 400 Hz) in the Zengmu Basin is primarily attributed to distant sources, commonly identified as ship radiation noise. In the high-frequency band (greater than 400 Hz), the marine ambient noise is primarily derived from the sea surface, predominantly in the form of wind-generated noise. In the frequency range of 25–1600 Hz, examined in this study, the power spectral density exhibits an average decrease of over 3 dB and a maximum decrease of over 5 dB with each doubling of frequency. When the frequency is below 400 Hz, there is a higher vertical spatial correlation to ambient noise. The vertical directivity of the noise energy is horizontal, meaning that it is perpendicular to the vertical array direction. Additionally, the probability distribution of the noise level approximately follows the Burr distribution. When the frequency exceeds 400 Hz, there is a low vertical spatial correlation to noise. The vertical directivity of environmental noise exhibits distinct grooves in the horizontal direction, and the probability distribution of the noise spectrum level generally follows a normal distribution.