Speed of Sound

How fast does sound travel in different media?

A simple model that explains the main factors affecting the speed of sound is a collection of balls (molecules) connected to each other by springs (bonds between molecules). Vibration from one ball will be transferred by the springs to neighboring balls, and in succession throughout the collection. The stiffer the springs and the lighter the balls, the faster the vibrations will be transferred. The springs are a model of the bulk elasticity (how the volume changes when the pressure on it changes) of the material, the balls and their spacing model the density of the material. In general, the speed is slowest in gases, fastest in solids. Even though liquids and solids are about 1,000 times denser than gases, the greater elasticity of liquids and solids more than compensates for the larger density. In gases the speed depends on the kind of molecule and temperature. For air, the speed depends only on temperature. The following table illustrates some examples of the speed of sound in different media.

Medium Speed (m/s)
Air (0°C) 331
Air (20°C) 343
Air (100°C) 366
Helium (0°C) 965
Mercury 1,452
Water (20°C) 1,482
Lead 1,960
Wood (oak) 3,850
Iron 5,000
Copper 5,010
Glass 5,640
Steel 5,960


This is a web preview of the "The Handy Physics Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App