SIREN

noisemaking device producing a piercing sound of definite pitch. Used as a warning signal, it was invented in the late 18th century by the Scottish natural philosopher John Robison. The name was given it by the French engineer Charles Cagniard de La Tour, who devised an acoustical instrument of the type in 1819. A disk with evenly spaced holes around its edge is rotated at high speed, interrupting at regular intervals a jet of air directed at the holes. The resulting regular pulsations cause a sound wave in the surrounding air. The siren is thus classified as a free aerophone. The sound-wave frequency of its pitch equals the number of air puffs (or holes times number of revolutions) per second. The strident sound results from the high number of overtones (harmonics) present. any member of the family Sirenidae (order Caudata), a group of three species of aquatic salamanders that resemble eels. Their long, slender bodies are usually brown, dark gray, or greenish. The forelegs are tiny, and the hind legs and pelvis are absent. Young and adults have feathery gills. Sirens usually burrow in mud in the bottom of marshes or streams or hide among water plants or stones, but sometimes they venture onto dry land for brief periods. Out of the water they can make a soft yelping or squeaking sound. Their principal diet is insects and small fish, which they catch at night. They mate in the water and lay eggs singly or in batches on the leaves of water plants. It is not known whether fertilization is internal or external. The young develop into adults without metamorphosis, or radical physical change, and some live at least 25 years or longer. The greater siren (Siren lacertina) is 5090 cm (about 2035 inches) long and occurs in the Atlantic coastal states of the United States from Delaware southward to Florida and westward to northern Mexico. The lesser siren (Siren intermedia) is about 1760 cm long and is found from South Carolina to Texas and in the Mississippi Valley northward to Illinois and Indiana. The dwarf siren (Pseudobranchus striatus), of which at least five races have been identified, is about 1221 cm long. Its range is throughout Florida and into southern South Carolina.