Siren types refer to the different categories of emergency vehicle sirens used to alert the public and other drivers. Common types include the wail, which has a rising and falling tone, and the yelp, characterized by a rapid, high-pitched sound. Each type serves a specific purpose, helping to convey urgency and ensure safety during emergencies. Another type is the hi-lo siren, which alternates between high and low frequencies, often used in certain regions for specific alerts. Additionally, some emergency vehicles may use a piercer siren, which produces a loud, penetrating sound designed to cut through ambient noise, ensuring maximum visibility and response.