Calculated Versus Observed Underwater Sound Speed Essay

Calculated Versus Observed Underwater Sound Speed - Essay Example The speed of sound in air is approximately figured out by the formula . . . speed of sound (m/s) = 331.5 + 0.60 T(C). The speed or velocity, at which sound travels through water was first researched by Sir Isaac Newton in 1687 when he found that measurements of sound in fluids relied only on the physical properties of the fluid, such as elasticity and density (Funk & Wagnalls). The speed of sound in water is about four times greater than that in air. Although this seems to contradict the physical law that the denser the gas, the slower the speed of sound, the sound speed is actually determined more by the elasticity of the medium (Urick, 1983). In 1822, Daniel Colloden used an underwater bell in an attempt to calculate the speed of sound underwater in Lake Geneva, Switzerland. His attempts resulted in figures remarkably close to today's accepted values (Acoustics . . . 2006). But sound speed cannot be discussed without mention of Jaque Sturm, French mathematician, who made the first accurate measurements of sound velocity in water in 1826. World War I created a great necessity to study the propagation of sound under water, with more progress in World War II and increased understanding from current research (Funk & Wagnalls). ... His attempts resulted in figures remarkably close to today's accepted values (Acoustics . . . 2006). But sound speed cannot be discussed without mention of Jaque Sturm, French mathematician, who made the first accurate measurements of sound velocity in water in 1826. World War I created a great necessity to study the propagation of sound under water, with more progress in World War II and increased understanding from current research (Funk & Wagnalls). The fact that sound moves in a straight line in a medium of equal density (ibid.) led to studies of water variables. Sonar's accuracy depends upon: 1. The reflection of sounds propagated in water. 2. Whether sound is reflecting or refracting. 3. Levels of salinity, while generally constant in the open ocean, greatly changes how sound travels through shallow water. 4. Temperature, a foremost factor in sound speed calculations, usually becomes lower at greater depths of water, decreasing sound speed at about 3 m/sec per degree Celsius. Below 1000m, though, temperature becomes generally constant and pressure is the predominant consideration. But a depth change of about 165m can cause the same change in sound speed as a one-degree temperature drop. Acoustic Tomography (a type of underwater CT scan) and Sofar Floats are examples of technologies and instruments that measure the movement of large scale ocean water mass. A unique feature of the ocean is the Sofar Channel in the upper regions of the deep ocean. In this layer of the ocean, at about 1250 meters below the surface in the northwest Atlantic, the temperature and pressure act to provide a "long range acoustic path or channel"(Acoustic . . . 2006). The SOFAR float is an instrument designed to be neutrally buoyant at a certain depth and