Fire/EMS Sirens and Speakers

Fire Truck Siren Sounds
Fire truck siren sounds and tone patterns can vary, depending upon the firefighter's objectives. Alternating tones of a fire truck siren may indicate the fire truck is approaching or passing through an intersection. A long, continuous fire truck siren tone can communicate to motorists or pedestrians that the roadway needs to be cleared immediately. 

The Need for Ambulance Sirens
Ambulance sirens are loud and are meant to grab the attention of motorists and pedestrians to communicate that an EMS (emergency medical services) team is responding to a medical emergency. Depending on the jurisdiction requirements, an ambulance siren can make various tone patterns, such as a wail, yelp, or air horn sound. Local regulations mandate permissible sound volume, ambulance siren tones, and under what circumstances an ambulance siren can be activated.