Water Depth and Speed of Sound
Name: Nevnariel A
Why is it that as sound waves pass from a deeper region to a
shallower region of water, their speed decreases?
The speed of sound in water depends upon several factors: depth,
At first the speed of sound decreases with depth (decrease in water
temperature), but at about 1000 m it begins to increase with depth because
the temperature becomes more or less constant but the pressure increases. As
a result at about 1000 m the speed of sound becomes a minimum. This creates
a "megaphone" effect where sound can travel for thousands of kilometers.
The speed of sound is dependent on the density of the medium -- and, in
general, sound waves travel faster through mediums that are more dense.
See for example, this web site, which lists the speed of sound for a variety
The deeper regions of water would be at a higher pressure (and therefore
more dense), so you would expect the speed of sound waves to be higher.
Here is a web site that explains some of the equations used to calculate the
speed of sound in seawater at various temperatures, salinities, and
Todd Clark, Office of Science
U.S. Department of Energy
Click here to return to the Physics Archives
Update: June 2012