Effects of rough surface on sound propagation in shallow water

Abstract

Underwater acoustic applications depend critically on the prediction of sound propagation, which can be significantly affected by a rough surface, especially in shallow water. This paper aims to investigate how randomly fluctuating surface influences transmission loss (TL) in shallow water. The one-dimension wind-wave spectrum, Monterey-Miami parabolic equation (MMPE) model, Monte Carlo method, and parallel computing technology are combined to investigate the effects of different sea states on sound propagation. It is shown that TL distribution properties are related to the wind speed, frequency, range, and sound speed profile. In a homogenous waveguide, with wind speed increasing, the TLs are greater and more dispersive. For a negative thermocline waveguide, when the source is above the thermocline and the receiver is below that, the effects of the rough surface are the same and more significant. When the source and receiver are both below the thermocline, the TL distributions are nearly the same for different wind speeds. The mechanism of the different TL distribution properties in the thermocline environment is explained by using ray theory. In conclusion, the statistical characteristics of TL are affected by the relative roughness of the surface, the interaction strength of the sound field with the surface, and the changes of propagating angle due to refraction.

The Effects of Bubble Scattering on Sound Propagation in Shallow Water

“…It is shown that the probability distribution at 200 Hz is more concentrated than 1000 Hz. This result is very similar to the probability distribution of TL under rough sea surface conditions [16]. Since the wavelength of 200 Hz is larger than 1000 Hz, the perturbation of the bubble plumes on the same scale is minor.…”

“…We analysed the sound field fluctuation and energy loss in the presence of bubble layers in two typical shallow-water environments, a homogenous waveguide and a waveguide with a negative gradient sound speed layer. To compare the effects of the bubble scattering and the rough sea surface scattering, the same environments as those in literature [16] were used. According to Figure 3b, there are evident sound speed changes caused by bubbles in the frequency band of 0.1 to 20 kHz.…”

“…Since previous studies have investigated high-frequency cases [9][10][11], this paper focuses on low-frequency ones. In order to compare with the effects of the fluctuant sea surface [16], we discussed the sound field at the frequencies of 200 Hz and 1000 Hz here.…”

EH-IRSP: Energy Harvesting Based Intelligent Relay Selection Protocol

“…The protocol works in cooperation based communication mode. This scheme employed Monterey-Miami Parabolic Equation (MMPE) [25] technique for communication channel modeling which is best suited for shallow waters and cannot be easily adopted in deep underwater environments. Table I shows the comparison of different state of the art cooperation based UWSNs protocols.…”

“…The aggregate path loss for EH-IRSP is 40dB while for EH-ARCUN the path loss is 60dB. The improvement in path loss for EH-IRSP suggests the efficient working of a passive sonar equation [20] in deep waters for EH-IRSP as compared to Monterey-Miami Parabolic Equation [25] employed in EH-ARCUN.…”