Visual and audible signalling systems are among the most important vehicle components both in terms of safety on public road as well as on private premises. Audible signalling can attract attention even when it is not within the field of vision or in the immediate vicinity of the road users concerned.
In order to quickly alert the general public to hazardous situations, e.g. in public road traffic, road users are made aware by special signalling systems on emergency vehicles both using colours (visual) and sound sequences (audible). People react more quickly to audible warning signals than to visual stimuli. This has evolutionary reasons because our ancestors were able to hear enemies before they saw them.
It is a matter of fact that a loud, sudden noise triggers physical reactions: the body gears up to make an escape and shows reactions of stress. For this purpose, it activates all the necessary sensory organs to be able to react quickly at any time.
According to the German definition in DIN 14610, a system that produces a "sequence of sounds of different fundamental frequencies" is called an "audible warning device for priority road users". This standard also determines, among other things, the frequency pitches and the sound sequence of the siren.
There are different warning signals depending on the country. In Germany today, a high and a low tone between 360 Hz and 630 Hz generate the typical German melody, which corresponds musically to a perfect fourth. In the USA and also in many other countries, the so-called "wail and yelp" signals are used. These are rising and falling howling sounds in different frequencies and pitches. Since 2013, the "Yelp" signal may also be used in Germany to attract attention in particularly dangerous situations.
The environment also influences the perceptibility of audible stimuli which is why there are different warning signals for urban and rural areas in Germany. In cities, a siren must be at least 110 decibels loud. In this case, the sound tends to be emitted within the immediate vicinity of the vehicle, as emergency vehicles tend to travel at a slower speed than in the countryside. In rural areas, the specified volume is lower. This is because there is less resistance in the form of buildings and sound waves can thus propagate further. In contrast, this siren’s sound waves are bundled and emitted towards the front.
You can find a compilation of audio samples of the sound sequences from different countries here.
Today HELLA is one of the leading suppliers for the most diverse requirements of emergency vehicles within the police, fire service and rescue services. With the RTK (roof bar) HELLA combines the two components "sound and light" and thus offers maximum safety. In addition to playing different audible signals and the classic blue light, today's RTK7 boasts other helpful, additional functions:
For more information about the RTK7 and its individual configuration options check here. The above-mentioned, different sound sequences are stored in the memory of the RTK7 and can be selected by country-specific programming.
In addition to the RTK7, HELLA's product range includes other reliable, safety-relevant products, for example electronic and electromechanical horns, visual warning systems, permanent signals and other warning lights.
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