Stentors are a type of large, trumpet-shaped protozoans found mainly in freshwater and marine environments. They are known for their distinctive loud voices, which they produce by rapidly flapping rows of cilia. Synonyms for stentors include trumpet animals, bellowers, horned protozoans, thunder beasts, and megaphone organisms. These organisms are often used as indicators of water quality, as their presence indicates a healthy ecosystem. Stentors play an important role in the food chain, serving as a food source for a variety of aquatic organisms, including fish and other larger predators. They are also important bioindicators of the health of aquatic environments and are used in research to test the effects of environmental pollution on freshwater and marine ecosystems.