The siren of an ambulance creates a loud sound created by forward firing speakers. This sound, called the ambulance tone is a landmark feature of every ambulance worldwide.
The volume of the siren can reach up to 140 decibels. This is as loud as a commercial aircraft taking off.
Without obstructions blocking the sound, the siren tone is able to reach a distance of 300 metres (96 feet) or 6 standard car lengths ahead at maximum volume.
Though startling, the range of the siren tone extends a commendable distance. This allows the traffic way ahead of the ambulance to be alerted early on.
|Volume in Decibels||Distance Siren Can Be Heard|
|140||300 metres / 96 feet|
|120||260 metres / 82 feet|
|100||215 metres / 68 feet|
|80||170 metres / 55 feet|
Disclaimer: Environmental factors such as nearby noise from traffic inevitably reduce the audibility of the ambulance sirens. The reduction could be as much as 80% in practical circumstances.
The ambulance driver is able to adjust the ambulance siren features via knobs installed within the vehicle cabin.
See the video GIF on how the siren tone can be changed is done:
This second video GIF shows how the siren is turned on:
The 3rd video GIF explains how the volume is adjusted with a simple knob:
The overhead barlight (mounted on the ceiling of the ambulance) as well as the flashing side lights (secured at the sides of the van) are also essential components of a functional ambulance. They increase visibility day or night.
Moreover, other drivers can give way quickly, while the ambulance crew do not have to solely rely on the siren.
There are 3 common ambulance sounds:
The sounds may seem to resemble English words but in fact they have no meaning.
The frequency (how fast) and volume (how loud) are also electronically set during the manufacturing of the siren.
Wail is the fastest among the three sounds. It feels the most urgent and panicky. Used in critical emergencies, the sound is sharp and piercing to the ears.
Yelp is the default tone. Used by ambulances in most of their operations, the yelp sound is meant to be an awareness tone. You can hear the sound grow louder as the ambulance comes toward you, and subsequently, softer as the ambulance drives past.
Hi-Lo is hardly used as it sounds the most childish. The music it makes is similar to the sound some toys make. Playing the Hi-Lo sound downplays the urgency and seriousness of the medical situation (from the informal feedback of ambulance crew).
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Don’t belittle the simple siren. The ambulance siren has bigger responsibilities other than merely playing back the siren tones on repeat. Ambulance speakers have specific requirements which make them different from your home theatre setup. The installation and configuration is custom-built based on the vehicle brand (example: Mercedes, Renault, etc).
For some ambulances, you won’t be able to hear the siren if you are to the sides or at the back of the ambulance.
To reduce excessive noise, updated ambulance fleets only install speakers under the front bonnet. This is instead of having speakers on all four sides of the van.
Sound emitted is only directed forward to alert vehicles ahead, whereas the vehicles following (or even tailgating behind the ambulance) will not be able to hear the siren at all. This updated design is developed and implemented with greater intent and functionality.
The volume of the siren is designed to fluctuate – louder and then softer. The loudness changes systematically in a sine wave pattern to create variation.
This change in volume is very noticeable and pings other drivers of the oddity.
The minimum and maximum volume of the ambulance siren varies between 140 decibels and 80 decibels.
For easy reference, 80 decibels is similar to the sound that air-conditioning unit makes. 140 decibels will be louder than a plane taking off.
Read more about ambulances in these articles:
This post was last modified on January 8, 2021 7:36 pm