l>Echosounding and also water depth

## Measuringwater depth: Echosounding

### Historical Note

Tomeasure ocean water depths before the advancement of echosounders, a heavy line to be lowered to theseafloor. The size of line the it took to reach the bottom to be measured andrecorded. This was dubbed "sounding". The H.M.S. Challenger is shownin the number to the right with a line over the side. The Challenger exploration which setsail in 1872 and lasted four years, was thought about the first purely oceanographicinvestigation. Throughout the expedition 492 soundings were made making use of a heavy line.

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### The speed of sound in the ocean

Soundings are currently made by sending a sound pulse into the water. To usage sound to measurewater depth we must know exactly how sound travels through the ocean. The speed of sounddepends on the temperature the the water, its salinity, and the pressure (which isequivalent come depth listed below the sea surface). The speed of sound ranges in between 1400and 1570 m/sec (4593 and also 5151 ft/sec). This is roughly 1.5 km/sec (just under 1mile/sec) or about 4 times faster that sound travel v air. The graph below shows howsound rate varies together a duty of water depth.

### Echosounders

Since civilization War II echosoundershave been provided to determine water depth in the oceans. Echosounders are attached tothe hull the a ship or a towed vehicle. An echosounder sends an outgoing sound pulseinto the water. The sound power travels v the water come the s bottom whereit is reflected back towards the source, received, and recorded.

The time that it takes for sound to make the round pilgrimage to the seafloor and back isaccurately measured. Water depth is established from the take trip time and also the rate of soundin water.Water depth have the right to be estimated simply by making use of an average sound speed and also the followingrelationship:Distance = rate multiplied by time/2The time is divided by 2 come account for the two-way expedition to the sea floor and back.

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