Not very long ago building a near-silent engine was a triumph that would have car manufacturers shouting from the roof-tops.
Those days, however, are passing fast. Vehicles are now so quiet that there are fears pedestrians and cyclists are at risk because they cannot hear them coming.
So governments in the Europe and the USA are considering plans that would force carmakers to turn up the volume again, by installing artificial noise generators.
Any vehicle that falls below the limit - believed to be around 40 decibels, or the level of a fridge motor - would be required to amplify its engine noise artificially.
The move would affect ordinary models, which have become much quieter in recent years, as well as electric cars.
It means the familiar purr of combustion engines could soon be replaced by futuristic electronic sounds. At present there is no lower limit for noise, only an upper limit to prevent excessive noise pollution.
Concerns about the silent danger of some vehicles were first raised after the introduction of electric cars and vans.
The idea of adding artificial noise was extended to diesel and petrol engines after research found some models were equally quiet at speeds under 32km/h.
Manufacturers have already started experimenting with different noises, from the roar of a sports car to bird song.
Last year Toyota announced it would begin selling a noise generator on its hybrid car, the Prius - producing a sound that some compared to a car in the Jetsons, the 1960s U.S. cartoon about a space-age family.
And Nissan took inspiration from Star Trek for its Leaf electric car, adding an optional noise generator that makes a swooshing sound like the Starship Enterprise. -Daily Mail