The art of car noise
1st Jan 2015 Technology
Like everything on a car nowadays, the sound of your engine isn’t left to chance. You’d have thought that the noise of an engine is just a result of the power under the bonnet, but the sound of a car—especially when accelerating—is such a defining part that manufacturers spend millions getting it right.
Does that mean the sound of a car is a recording?
For smaller cars, there’s light audio tuning to make sure the engine is unobtrusive while still giving you enough audio feedback to help with gear changes and suchlike. But the chassis of premium sports cars are so effective at cutting out unwanted road hiss that engine sounds become muted, too. How to put the sporty sound back? With a lot of engineering effort is the answer.
The new Ford Focus ST hot hatch has a system to ensure the engine is quiet when you want, but raucous under acceleration. The car features a specially engineered tube from the engine to the back of the dashboard; drop the accelerator and it opens to double the sound of the turbo-charged engine.
Even the current Porsche 911 has a Sound Symposer as part of the exhaust. It includes a diaphragm that’s activated when the car is put in sport mode, which amplifies the sound of the engine inside and out without exposing you to all that messy road noise.
BMW takes this a stage further with its Active Sound Design technology. In the latest M5 super-saloon, the car produces a pre-recorded engine noise as you hit the accelerator. The artificial noise follows the scream of the real 560hp engine and plays out through interior speakers. Not even the classic VW Golf GTI is immune from this audio tweaking—since 2011, the car has had an artificial vibration device behind the dashboard called the Soundaktor, which adds to the engine buzz under hard acceleration.
Of course, full electric cars change all this because they make virtually no sound—not great if you’re a cyclist or pedestrian. Progressive car companies are looking at generating artificial sounds for electric cars so people know they’re coming. Some are experimenting with artificial engine noises (Audi), while others are looking at totally new kinds of sound—beeps, whines and the like. What would you want to hear?