where is the speed of sound is maximum
Speed of sound In common everyday speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: sound travels most slowly in gases; it travels faster in liquids; and faster still in solids. For example, (as noted above), sound travels at 343 m/s in air; it travels at 1,484 m/s in water (4.3 times as fast as in air); and at 5,120 m/s in iron (about 15 times as fast as in air). In an exceptionally stiff material such as diamond, sound travels at 12,000 metres per second (26,843Â mph);[1] (about 35 times as fast as in air) which is around the maximum speed that sound will travel under normal conditions.
Train horn On April 27, 2005, the Federal Railroad Administration (FRA), which enforces rail safety regulations, published the final rule on the use of locomotive horns at highway-rail grade crossings.[4][5] Effective June 24, 2005, the rule requires that locomotive horns be sounded at all public grade crossings at least 15 seconds, but not more than 20 seconds before entering a crossing.[6] This rule applies when the train speed is below 45 mph (70 km/h). At 45 mph or above, trains are still required to sound their horn at the designated location (usually denoted with a whistle post).