The speed of sound in dry air is approximately 344 meters per second, or 770 miles per hour. This assumes dry air at sea level with a temperature of 68 degrees Fahrenheit.
Unlike the speed of light, the speed of sound is not a constant and is affected by the medium through which it travels. Differences in atmospheric temperature and pressure cause variations in the speed of sound. Sound waves travel faster in liquids and non-porous solids than they do in air. In fresh water at 77 degrees Fahrenheit, sound travels at about 1497 meters per second, or nearly 3,350 miles per hour.