Editing Ambulance (section)

===Audible warnings===
{{Main|Emergency vehicle equipment#Audible Warning Devices (Sirens)|l1=Audible warning devices}}

[[File:Whelen.ogg|thumb|right|A [[Whelen Engineering Company]] siren with ''wail'', ''yelp'' and ''phaser'' tones, commonly used by [[emergency vehicle]]s such as ambulances in several countries]]
In addition to visual warnings, ambulances can be fitted with '''audible warnings''', sometimes known as [[siren (noisemaker)|siren]]s, which can alert people and vehicles to the presence of an ambulance before they can be seen. The first audible warnings were mechanical bells, mounted to either the front or roof of the ambulance. Most modern ambulances are now fitted with electronic sirens, producing a range of different noises which ambulance operators can use to attract more attention to themselves, particularly when proceeding through an intersection or in heavy traffic.<ref>{{cite book|others=The Canadian Red Cross|title=Emergency Care Manual|publisher=The StayWell Health Company|location=Guelph, ON|year=2008|page=359|chapter=23|isbn=978-1584804048}}.</ref>
[[File:St John ambulance Dunedin.jpg|thumb|A [[Hato Hone St John]] responding through traffic in [[New Zealand]]]]
The speakers for modern sirens can be integral to the lightbar, or they may be hidden in or flush to the grill to reduce noise inside the ambulance that may interfere with patient care and radio communications. Ambulances can additionally be fitted with [[airhorn]] audible warnings to augment the effectiveness of the siren system, or may be fitted with extremely loud two-tone air horns as their primary siren.

A recent{{when|date=February 2024}} development is the use of the [[Radio Data System|RDS]] system of [[Car audio|car radios]]. The ambulance is fitted with a short range [[Frequency modulation|FM]] transmitter, set to RDS code 31, which interrupts the radio of all cars within range, in the manner of a traffic broadcast, but in such a way that the user of the receiving radio is unable to opt-out of the message (as with traffic broadcasts).<ref>{{cite web|url=http://www.freepatentsonline.com/y2003/0164775.html|title=Emergency warning device – patent application|access-date=19 November 2009}}</ref> This feature is built into every RDS radio for use in national emergency broadcast systems, but short-range units on emergency vehicles can prove an effective means of alerting traffic to their presence. It is, however, unlikely that this system could replace audible warnings, as it is unable to alert pedestrians, those not using a compatible radio or even have it turned off.<ref>{{cite book|last=Wright|first=Scott|title=The Broadcaster's Guide to RDS|publisher=Butterworth-Heineman|location=Woburn, MA|year=1997|page=73|isbn=0240802780|url=https://books.google.com/books?id=MX0nKoHTQ_4C&q=RDS%20Code%2031&pg=PA47}}</ref>