Imagine a whale is swimming through the ocean and calls out to its pod. The whale produces sound waves that move like ripples in the water. Once the sound waves reach the bottom of what is known as the thermocline layer, the speed of sound reaches its minimum. But the fact that sound travels faster in water than in air just brings up the next question: Why is it harder to talk to someone underwater than in air?
The answer is that sound couples poorly from air to water. When you talk, you do so by emitting air and then sending compression waves through this air.
Your lungs provide the burst of air, and your vibrating vocal cords and mouth imprint the appropriate sound waveform on the air. In order for someone underwater to hear you, the sound waves have to go from the air in your mouth into the water surrounding you.
Sound waves have a hard time going from air into water and mostly get reflected at the air-water interface instead of being transmitted into the water. If your lungs and airways were filled with water, and if your vocal cords and lungs were tuned to handle water, you would do a better job of generating sound underwater as there would no longer be an air-water interface.
Topics: compression wave , reflection , sound , sound wave , sound waves , speed of sound , stiffness , water , wave , waves. The SOFAR channel is important because sounds produced in that region can be propagated over very long distances with little attenuation loss of energy. Sound waves produced in the channel radiate out in all directions. Waves that travel into shallower or deeper water outside of the sound channel are entering a region of faster sound transmission. As we saw with seismic waves, when these sound waves encounter a region of differing transmission speed, the waves tend to be refracted or bent back towards the region of lower speed.
As a result, sound waves moving from the SOFAR channel into shallower water will be refracted back towards the channel. As the sound waves go deeper below the channel, they will be refracted upwards, back into the channel and the region of slower speed. In this way, much of the sound does not dissipate out into the water in all directions, but instead is trapped within the channel, and can travel very long distances with little loss of energy Figure 6.
Baleen whales are thought to use the SOFAR channel to communicate with each other over long distances of hundreds to thousands of kilometers. Their vocalizations are very loud and are low frequency calls, which travel farther than high frequency sounds in the oceans.
A stranded pilot could drop a small device into the water, and once it sank into the SOFAR channel it would explode, creating a sound that could be heard at multiple listening stations. Using the time of arrival of the sound at the various receivers, the location of the source could be determined through triangulation. Use of Sound How do marine animals use sound? Marine Mammal Communication Individual-specific Vocalizations Group-specific Vocalizations Vocalizations Associated with Reproduction Sounds Associated with Aggression Marine fish communication Marine invertebrate communication Marine mammals feeding Marine fish and invertebrates feeding Marine mammal navigation Sound Production How do marine mammals produce sounds?
How do fish produce sounds? How do marine invertebrates produce sounds? Sound Reception How do marine mammals hear? How do aquatic birds hear? How do fish hear?
How do marine invertebrates detect sounds? How did odontocete hearing evolve? How is sound used to measure water depth? How is sound used to find objects on the ocean bottom? Fishing How is sound used to locate fish? How is sound used to identify fish?
Communications How is sound used to communicate underwater? How is sound used to transmit data underwater? Research Ocean Physics How is sound used to measure temperature in the ocean? How is sound used to measure global climate change? How is sound used to measure currents in the ocean? How is sound used to measure waves in the surf zone? How is sound used to measure the upper ocean?
How is sound used to help make long-term measurements of the ocean? How is sound used to explore for oil and gas? How is sound used to measure, detect, and track oil? How is sound used to study undersea earthquakes? How is sound used to study underwater volcanoes? How is sound used to map the seafloor? How is sound used to research wind energy?
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