The term 'Steam Whistle Sound' can be summarized as 'TOOT', which is a four-letter word. A steam whistle sound is a loud, shrill sound made by a steam engine or locomotive, usually to signal the start or end of a journey. It is also used to warn people of danger or to signal the arrival of a train. The sound is produced by the release of steam from a whistle, which is usually mounted on the roof of the locomotive.