There is almost a romantic appeal to police car sirens in movies when you see the cops involved in a high-speed chase that culminates in the bad guys being arrested and the good guys being saved. In real life, though, the wailing of sirens on police cars is usually not a good sign, for more often than not, it signifies that there has been some trouble or crime that the police is attempting to tackle.

Apart from police vehicles, sirens and lights are also used by the fire brigade and ambulances. After all, each of them is working to address what may well be a life-and-death situation. From a practical standpoint, police car sirens and lights serve one basic purpose: that of warning bystanders or people around a crime scene to make way so that trained professionals can take over and do whatever is needed. If a crime has been committed, sirens can also serve to warn the perpetrators that the long arm of the law is snapping at their heels. Such a warning may sound counter-intuitive; but the fear of being caught often forces the perpetrators to make mistakes and get caught or leave valuable clues. Almost like the sirens described in Greek mythology- 3 bewitching women who would call out to sailors from the rocks and cause their ships to be wrecked. Interestingly, there is a similar story in Germany too- that of Lorelei.

For them to be effective, police car sirens must possess many features and characteristics. They must be loud and distinctive. For the technically orientated, the sound emitted by sirens is measured in dB (decibels). Equally important is how much electricity they draw. Usually, police sirens are connected to the car battery or similar source of DC. If one were to go into the physics of a siren, it converts electrical energy into sound energy. Some sirens are mounted on top of the vehicle; others are mounted on the dashboard. In the former category, there is no obstacle to the sound waves, while in the latter case, the walls and floor of the car, the upholstery and even the people inside, act as obstacles. This can damp the amplitude of the sound, in turn affecting how far it is heard. There is another reason why sirens should ideally not be mounted inside the car. This has to do with the risk of damage to the hearing of those inside the vehicle because of the high level of noise generated by a siren for sustained periods of time. That is why regulations even specify that sirens must be mounted in a particular way- parallel to the road surface and parallel to the direction in which the vehicle is travelling.

Like with other electronic and electrical devices, cheap imported police car sirens too have flooded the market. But when you are looking to buy something as important to the well-being of society as a police siren, a higher price is justified for greater product quality, reliability and safety. Make sure also that the sirens you decide to buy are approved by the relevant government agencies.

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