When John Robison invented the siren in Scotland in the 1790s, he intended it for use as a musical instrument. It was modified and improved by Charles Cagniard, who created a siren that could produce sound and be heard underwater. These early sirens were pneumatic and were powered by differences in air pressure; air rushing through small holes intermittently produced the characteristic siren sounds that are still familiar today. Steam whistles were an early form of siren and were used on trains and in factories to serve as a signaling device as early as the 1830s; they were also incorporated into lighthouses to provide additional warning of the nearby coastline for ships at sea. It was not until the early 20th century, however, that sirens would be commonly used as warning devices, and even later before they were incorporated into emergency vehicles as an additional alert to drivers and pedestrians.
Today, sirens play a vital role in police, fire, and other emergency responses. Sirens provide an audible warning of oncoming emergency vehicles, which may be traveling at high rates of speed, and send a clear message to nearby traffic and pedestrians to pull over and allow these public safety workers to pass safely. While many pneumatic or mechanical sirens are still in use today, more and more modern police, fire, and ambulance services use electronic sirens to alert the public to their presence and approach. Advanced circuit-based technology allows the frequency and volume of the siren to be controlled precisely and often allow the emergency vehicle personnel to decide on which tone pattern will be most effective in a particular situation.
Caution should be used with certain siren devices, since they can produce sound loud enough to temporarily deafen those nearby if not properly modulated. This is especially true of concealed or partially recessed sirens, which often create a great deal of sound inside the cabin of the emergency vehicle and can cause hearing problems for first responders who receive prolonged exposure to siren noise. Properly shielded and positioned sirens produce much less noise inside the passenger compartment and provide better advance warning to the public as well. The staff at Extreme Tactical Dynamics can advise your agency on the correct positioning and most appropriate and useful sirens for your specific needs.