Poikonen Ari, Madekivi Seppo
Finnish Naval Research Institute, PO Box 116, FIN-02631 Espoo, Finland.
J Acoust Soc Am. 2010 Jun;127(6):3385-93. doi: 10.1121/1.3397364.
Underwater ambient noise measurements were carried out in a shallow (15-20 m) brackish water in the archipelago of the Gulf of Finland for period of 1 year. The absence of traffic noise made it possible to study wind driven effects in ambient noise at lower frequencies. The ambient noise comes mostly from local sources and the propagation effects are shown to be negligible. The ambient noise develops bubble type spectral features above 100 Hz as wind speed increases. Sharp spectral declines are observed below 500 Hz, which are most likely due to resonances from oscillating bubble clouds created by breaking waves. The low frequency range of the observed declines may partly be attributed to the larger bubble size in fresh and brackish waters. In the present study the wind speed dependence factor was approximately 2.4 at 200 Hz, which is significantly higher than the typical factor of approximately 1.5 for the ocean environment. The average high-frequency spectral slope was -4.9 dB/octave which is approximately 1 dB/octave less than for typical deep water slopes. No significant seasonal effects were found in any parameter calculated from the ambient noise spectra.
在芬兰湾群岛的浅（15 - 20米）咸淡水中进行了为期1年的水下环境噪声测量。由于没有交通噪声，使得研究低频环境噪声中的风驱动效应成为可能。环境噪声大多来自本地声源，且传播效应可忽略不计。随着风速增加，环境噪声在100赫兹以上呈现出气泡型频谱特征。在500赫兹以下观察到明显的频谱下降，这很可能是由于破浪产生的振荡气泡云的共振所致。观测到的下降的低频范围部分可归因于淡水和咸淡水中较大的气泡尺寸。在本研究中，200赫兹时风速依赖因子约为2.4，显著高于海洋环境中约1.5的典型因子。高频频谱平均斜率为 -4.9分贝/倍频程，比典型深水斜率约小1分贝/倍频程。从环境噪声频谱计算出的任何参数均未发现明显的季节效应。
