Diffuser (breathing set part)
Encyclopedia
A diffuser is a device fitted over an underwater breathing set
's exhaust hole to break up the resulting bubbles small so they will not be seen from out of the water, and make less noise (see acoustic signature
). They are used in:
Designing an adequate diffuser on a rebreather
is much easier than on open-circuit scuba.
A system was shown on a Discovery Channel
documentary about diving with hammerhead shark
s at Cocos Island
, Costa Rica
. Eddie Paul
designed—and in the early 1990s underwater photographers John McKenney and Marty Snyderman tested—a system they called the "scuba muffler
", for open-circuit scuba. This system had two large filter stones on the back of the tank with a hose connected to the exhaust ports of the second stage regulator. The two filter stones were mounted on a hinged arm to float 1 to 2 ft (30.5 to 61 cm) above the diver, to set up a depth-pressure-differential suction effect to counteract the extra exhalation pressure needed to breathe out through the diffuser. The scuba muffler cut the exhalation noise by 90%. Closed circuit rebreathers proved more useful in letting divers get near sharks.
Scuba set
A scuba set is an independent breathing set that provides a scuba diver with the breathing gas necessary to breathe underwater during scuba diving. It is much used for sport diving and some sorts of work diving....
's exhaust hole to break up the resulting bubbles small so they will not be seen from out of the water, and make less noise (see acoustic signature
Acoustic signature
Acoustic signature is used to describe a combination of acoustic emissions of ships and submarines.-Contributing factors:The acoustic signature is made up of a number of individual elements...
). They are used in:
- Combat diving (see frogmanFrogmanA frogman is someone who is trained to scuba diving or swim underwater in a military capacity which can include combat. Such personnel are also known by the more formal names of combat diver or combatant diver or combat swimmer....
), to avoid detection by surface guards or by underwater hydrophoneHydrophoneA hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change...
s. - Mostly, in underwater mineNaval mineA naval mine is a self-contained explosive device placed in water to destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, an enemy vessel...
operations conducted by clearance diverClearance DiverA clearance diver was originally a specialist naval diver who used explosives underwater to remove obstructions to make harbours and shipping channels safe to navigate, but later the term "clearance diver" was used to include other naval underwater work...
s, to make less noise, as acoustic mineAcoustic mineAn acoustic mine is a type of naval mine which monitors audio activity in its vicinity. Depending on its design, it will either actively send out audio pulses, not unlike a sonar, listening to the speed at which the echo returns to it or passively listen to its environment, depending only on the...
s are designed to explode when they detect particular sounds. - In marine biologyMarine biologyMarine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
, to avoid disruption of fish behavior.
Designing an adequate diffuser on a rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
is much easier than on open-circuit scuba.
A system was shown on a Discovery Channel
Discovery Channel
Discovery Channel is an American satellite and cable specialty channel , founded by John Hendricks and distributed by Discovery Communications. It is a publicly traded company run by CEO David Zaslav...
documentary about diving with hammerhead shark
Hammerhead shark
The hammerhead sharks are a group of sharks in the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a "cephalofoil". Most hammerhead species are placed in the genus Sphyrna while the...
s at Cocos Island
Cocos Island
Cocos Island is an uninhabited island located off the shore of Costa Rica . It constitutes the 11th district of Puntarenas Canton of the province of Puntarenas. It is one of the National Parks of Costa Rica...
, Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
. Eddie Paul
Eddie Paul
Eddie Paul is an American now residing in El Segundo, CA. He holds a few U.S. patents and is currently owner of E.P. Industries, Inc. E.P. Industries includes Prototech Machine Engineering, a CNC machine shop....
designed—and in the early 1990s underwater photographers John McKenney and Marty Snyderman tested—a system they called the "scuba muffler
Muffler
A muffler is a device for reducing the amount of noise emitted by the exhaust of an internal combustion engine. A US Patent for an Exhaust muffler for engines was granted to Milton and Marshall Reeves in 1897....
", for open-circuit scuba. This system had two large filter stones on the back of the tank with a hose connected to the exhaust ports of the second stage regulator. The two filter stones were mounted on a hinged arm to float 1 to 2 ft (30.5 to 61 cm) above the diver, to set up a depth-pressure-differential suction effect to counteract the extra exhalation pressure needed to breathe out through the diffuser. The scuba muffler cut the exhalation noise by 90%. Closed circuit rebreathers proved more useful in letting divers get near sharks.