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Animals that Produce Sounds in the Ocean
A great number of animals create sounds that travel through the ocean. Some animals vocalize these sounds -- as humans do -- above water. These include sea lions, walruses and polar bears. Underwater, the ocean is also alive with sounds produced by many types of animals, including mammals, crustaceans and fish. Whales and dolphins are the most proficient at producing a wide range of sounds, producing noises such as whistles, clicks and other sounds that are associated with the whale song.
How Sounds are Produced
Crustaceans produce underwater noises through quick movements of a large claw that causes air bubbles to form and burst, which in turn produces sound. Some animals, such as dolphins, produce underwater sound through the air pockets in their heads and nasal systems; they force air to move inside these pockets, which then resonates. Fish create vibrations in an internal organ that is filled with gas, causing sound waves to travel through water. Other animals simply slap water with their fins.
How Sound Travels in the Ocean
Sound can travel through a substance in any state -- gas, liquid or solid -- with varying levels of effectiveness. To create sounds in the ocean, waves of energy alter the pressure of the ocean water and these changes in pressure are detected by the ear. Ocean water is a very effective conduit for carrying sound, allowing sound waves to travel further and at a greater speed than they would through the air, as water has a greater density. However, while sound travels through water more easily than air, it is more difficult to hear sound underwater because of the way in which the ear detects sound.
How Animal Sounds are Heard in the Ocean
When sound waves are detected by the eardrum, bones in the inner ear vibrate, causing fluid and sensory hairs within the inner cavity of the ear to also vibrate. Signals are then sent along nerves to the brain so that we may detect the information as sound. Ocean mammals and most fish detect sound the same way. Below the surface of the ocean, it is much harder to hear sound, as this whole process is far less effective when the outer part of the ear becomes filled with water. To overcome this, marine animals often detect waves of sound by more effective methods than the human outer ear. Some fish detect sound initially through pores that run along the body and connect to one long cavity filled with sensory hairs similar to those in the ear. This action sends information along nerves to the brain. Other marine animals detect sound through an enclosed pocket of air within their bodies that becomes compressed by sound waves, creating vibrations that are sent to the inner ear.