The emergency signal consists of a light signal (blue and red flashing) and an audible signal. Accordingly, the audible signals are an integral part of the signal. The loudspeaker enables the car to detect the siren as soon as possible, thus helping it to move, and requires an appropriate volume, i.e. sound pressure.
Emergency signal loudspeakers ensure a long service life for the user, as they are subjected to numerous tests by the manufacturers. These include, for example, dust and water resistance, low and high temperature resistance, salt resistance and vibration tolerance.
Minimum sound pressure required for emergency acoustic signals
A vehicle entitled to use an mergency light and audible warning device shall also be fitted with an audible warning device for the purpose of giving a distinctive audible warning, which shall give an audible warning at a variable pitch, measured at a distance of 7 m in front of the vehicle, with a sound pressure level of between 103 dB(A) and 120 dB(A) per audible tone. The detailed phonetic requirements and the conditions for testing and qualification of the audible warning device fitted to a motor vehicle shall be laid down in a standard.
Hungarian Standard 07-4009:1982 provides for the required sound pressure level of the audible warning device, in this case the blue police flashing light. According to the standard, the maximum sound pressure level to be measured should be 0,5-1,5 m from the ground. In the area opposite and at an angle of 45 degrees to the vehicle, the sound pressure level should be 103dB(A), and at 90 degrees from the vehicle, from the side, a minimum of 98dB(A) should be measured within a radius of seven metres. The maximum sound pressure level shall not exceed 120 dB(A). If these are not met, the vehicle shall not pass the sound pressure measurement.
Fixing of the loudspeaker
The siren loudspeaker may be mounted in the light-bridge or in the engine compartment driven by the siren control. Nowadays, LED light bridges are so narrow that a loudspeaker can no longer fit in them, and therefore the placement in the engine compartment of the vehicle has become the preferred option. From the user's point of view, there is a significant difference between placing the loudspeaker in the light bridge or in the engine compartment, as the driver is not so sure whether the siren is directly above him or in the soundproofed engine compartment. Self-contained speakers are available in different sizes and mountings to facilitate installation in the engine compartment. If required, it is also possible to install speakers with a power of 100W or 200W, which requires the use of an amplifier with the corresponding power.
IRM Decree 12/2007 (III.13) is responsible for the rules on the installation and use of warning and warning signal transmitters.