Oceanic Sounds in a Realm of Silence
(A noisy silence in the waters of the oceans and the seas)
There is much more noise in the seas and oceans than we realize!
Far from being silent, the oceans have much more noise from the contributions of all kinds of creatures; such as, clicks, wheezes, whines, rumbles, scrapes, and bumps.
Just the whales alone send echoes of their songs across the oceans, utilizing a natural communication channel 1,000 meters (3,300 feet) beneath the surface. The roar of the surf, the rustle of sand, raindrops spattering on the surfaces of the oceans and seas, or the nibbling sounds of fish grazing on algae can all be heard with amazing clarity in the underwater world.
The cacophonies of the oceans are all amazing in that fish, mollusks, and crustaceans have no vocal chords to help them produce sounds. Instead of vocal chords, fish of the "grunt" family grind together their ukpper and lower pharyngeal teeth, located deep in their throats, to send out a sound which is similar to that of pigs when they are eating.
Croakers and drummers are also appropriately named, vibrating strong muscles attached to the swim-bladder walls. Similar to a guitar's sound-box, the bladder allows resonance and amplification, while the rates and natures of vibrations result in noises of different pitches, from deep thumps to higher clicks.
The toadfish, in addition to grunting, has achieved the sounds of boat whistles which are long, low-frequency bursts of sounds used primarily during the mating season.
Oceanic sounds travel faster and farther than they do out of the water
All sounds in the ocean; as well as, the the displacement effect on water caused by animal movements, are transmitted by compressive wave motion far more effectively underwater than in normal air conditions.
As a result, sound travels twice as far in water, and about four times farther. The audible, or sonic range for humans is between twenty and 20,000 Hz (herz, or cycle per second).
Lower frequencies are known as infrasonic, while higher frequencies are referred to as ultrasonic. Marine animals have a variety of auditory and pressure sensor for picking up these signals; lobsters have receiving antennae, crabs are sensitive to ground vibrations, while fish have both an inner ear and a lateral line.
Water creatures have external or internal receptions of sounds and some utilize both methods
Even without an external ear to capture and amplify signals, the inner ear in some fish can detect sound vibrations up to several kilometers away, while just below the surface of the skin is a system of mucus-filled canals containing flexible nerve endings that extend the length of the fish; known as the "lateral line".
Infrasonic vibrations, or pressure differences, cause the fluid in the canals to move and distort the nerve endings. Fish are very aware of the least movement underwater, whether the sea is crystal-clear or dark and murky.
Dolphins are able to find objects by means of echolocation. Sounds are produced in the nasal passages, then focused and sent out by the melon, a fatty organ in the forehead which functions as an acoustic lens.
Returning sound waves are channeled through oil-filled sinuses in the lower jaw to the inner ear, which is insulated from extraneous resonances within the skull.
A cross reference of ocean words.
A cross reference of "sound" or sono- words.