The car horn is celebrating its 100th anniversary. It’s one of the few car parts that have stayed virtually unchanged over the decades. Originally invented in Germany, it reveals a lot about how people communicate in countries around the world.
Dubai, May 3, 2015: What does a BMW, MINI, Rolls-Royce or, shall we say, any car sound like when it beeps? Remember? That loud, penetrating, clear tone? And yes, in any vehicle type it is indeed the same kind of sound because the signaling devices that make it are industrial modular systems. That means every vehicle producer essentially uses the same one. “Vehicle horns consist of a high tone and a low tone. Together they put out between 93 and 95 decibels at a distance of seven metres,” explains Peter Heinrich, test engineer at BMW for car horns. “That’s what the law specifies.”
These components do indeed make a fair amount of noise (the pain threshold for the human ear is about 130 decibels), and it’s a legal requirement for them to do so. Without an acoustic warning system, a vehicle is not allowed to take to the roads. “For us as a carmaker the horn is not really the focus of what we do, but in legal terms, it’s an important warning signal for road users,” says Heinrich.
Around the world car horns are used in very different ways. In India, for instance, motorcyclists and rickshaw, truck and car drivers honk every time they are about to start a manoeuvre. From turning off to overtaking or pulling away, each time an audible “toot” proclaims action is imminent. “Normal electromechanical car horns like the ones you find in Western vehicles wouldn’t last more than two or three months in India or China,” says Heinrich. “The coil would just burn through.” That’s why carmakers install electric ones in vehicles for frequent-use markets. They may be more expensive, but with a lifetime of about a million beeps they tend to last as long as the car itself. A standard Western variant, on the other hand, will honk a mere 50,000 times.
As a note of caution: In countries like those in Europe or North America, too much noise-making can cause the contact to burn through. Who’d have thought it? So the next time you celebrate on the streets because your best friend has finally got married or your local team has won at football, it’s best not to cause too much of a cacophony. “Beeping for more than about 90 seconds can push an electromechanical horn to its limits,” Heinrich explains.
Unspectacular as the humble horn may be for a vehicle producer, it is nonetheless the one part that has remained unchanged for the last 100 years. It works by using an electric current to vibrate a diaphragm, which then forces air through a sonic horn. The first electrical audio warning signal was registered by Robert Bosch in 1914 under the name of “Bosch-Horn” – and it was a massive success. By 1941 its inventor had sold 5 million units, thanks in part to its perfectly measured, pleasant sound, which was loud enough not to be overheard but not so noisy it would frighten the horses out on the streets. Moreover, this particular invention had a refined additional feature: adjustable volume. This meant it could be suited to urban or rural environments.
Fanfare behind the radiator grille
So where exactly does the component we’re talking about tend to hide? Have you ever seen the signaling device in your car? Suffice it to say that more often than not this component has to make do with whatever space is left in the front of the vehicle. Some are consequently mounted right behind the radiator grille. Others are fitted to the side members of the chassis or in the wheel arch. So depending on type and position, car horns sound different in different vehicles – even though they’re all made by the same supplier.