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Propagation I: Observations and Physical Models
Published in Paul C. Etter, Underwater Acoustic Modeling and Simulation, 2017
The deep sound channel, sometimes referred to as the sound fixing and ranging (SOFAR) channel, is a consequence of the sound-speed profile characteristic of the deep ocean (see Section 2.3). This profile has a sound-speed minimum at a depth that varies from about 1000 m at midlatitudes to near the surface in polar regions. This sound-speed minimum causes the ocean to act like a lens: above and below the minimum, the sound-speed gradient continually refracts the sound rays back toward the depth of minimum sound speed. This depth is termed the axis of the sound channel (refer back to Figure 2.7). A portion of the acoustic energy originating in the deep sound channel thus remains within the channel and encounters no losses by reflection from the sea surface or the sea floor. Sound in this channel will be diminished by the effects of absorption. The properties of the deep sound channel were first investigated by Ewing and Worzel (1948). The exceptional ducting characteristics of this channel have been used to advantage by oceanographers in the design and conduct of acoustic tomography experiments (see Section 6.10).
Fundamentals of underwater acoustics
Published in Frank Fahy, John Walker, Fundamentals of Noise and Vibration, 2003
Because of the geometrical effects outlined in section 7.2.2.4(a), acoustic signals will propagate to long range in the SOFAR channel. This facility has been exploited over the years in many ways, which are detailed in the references given at the start of the chapter, and as such will not be considered here. However in recent years a new technique has arisen which exploits this effect, Acoustic Thermometry of Ocean Climate (ATOC), and this will be discussed briefly. For further details see, for example, Munk and Baggcrocr (1994), which is an introductory article to a further seventeen papers in the same volume.
All-terminal reliability of multi-AUV cooperative systems in horizontally stratified SOFAR channel
Published in Ships and Offshore Structures, 2020
Qingwei Liang, Junlin Ou, Zengxi Xue
The transmission loss is one of the important factors that influence the performance of underwater acoustic communication in SOFAR channel. Underwater acoustic communication propagation distance and the available bandwidth of channel are severely limited by the transmission loss (Geethu and Babu 2017). The transmission loss is the loss of signal strength of underwater acoustic signal caused by wave front extension, absorption, and other factors in the communication process (Gao and Li 2010). Based on the Kraken normal mode (Chen et al. 2010; Santos et al. 2016; Kumar 2017) in horizontally stratified SOFAR channel, it can get the wave-pressure field solution easily, and then calculate the transmission loss of sea channel.