In Depth

Music to your gears: The art of a car's engine sound

Where's the fun in a silent supercar? Josh Sims extolls the importance of that distinctive, powerful roar

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"This is a Maserati," announces a radio advertisement from the Italian sports-car manufacturer. What is conspicuous about this ad, however, is that it gives so few details about the car in question. Rather, it is reduced to just 30 or so seconds of engine sound. This distinctive throaty roar is, the ad implies, all you need to know.

Maserati is not alone in this thinking. Engine note has become a significant brand statement and "vital in expressing a car's character and the company's emphasis on performance", says Nicola Boari, Ferrari's head of product marketing. "Each model is individually engineered to give it a recognisable sound, just like a musical instrument. The sound is taken into consideration from the moment we start to engineer a new engine."

Certainly, Steve Arnott's job has taken a turn. Aston Martin's powertrain sound-quality expert – a man with a background in acoustics rather than cars – began his career designing exhaust systems to make them quieter, which is precisely what most non-supercar drivers want.

"But in doing that you learn how to work with resonance in the pipes to make a certain note," explains the man behind what the company is calling its new DB11's "sonic identity". "Engines all produce the same frequencies, so it's about emphasising some over others, just as singers do. For a car brand to have a distinctive engine sound is just as important."

In broad strokes, he cites the distinction between the "very racy, high-revving, screaming sound" of Italian sportscars versus the "low and rumbling" sound of US supercars, placing Aston Martin's "gravelliness" somewhere in the middle. But developing a more precise brand sound is, of course, more complex than these descriptions allow for.

At Aston Martin, the marketing department will suggest the kind of sound it wants from a proposed car, then independent juries are used to assess preferred sounds "blind" – including those of competitor companies – and advanced simulation tools are used to work out if such a sound can be achieved with the engine.

After this effort, it's no wonder makers want drivers to be able to hear this mechanical music. In developing its LFA, for example, Lexus worked with Yamaha – the instrument-maker, not the engine-builder – to help develop components that direct engine sound to the cabin. With Ferrari's front-engined cars, in which the engine is relatively more distant from the cabin and isolated by the front bulkhead, special tubes are used to channel a small amount of sound from the intake plenum to the cabin.

Ferrari stresses the sound of its engines is never enhanced, but this is not always the case for other manufacturers. BMW, for example, has found the chassis of its M5 so effective at isolating the cabin from outside noise that it chose to play an exterior recording of the engine through the car's stereo, the precise sample played selected according to RPM. Porsche's "Sound Symposer" is a tube housing a diaphragm and a valve that, in sport mode, opens to amplify the engine sound. Closed, it allows for quieter cruising. More such systems might well be expected from other carmakers.

Indeed, although the advent of an all-electric supercar may be some time away, perhaps engine sound will one day be silenced for good. However, the industry is considering the need for electric cars to generate some kind of sound – as a warning to pedestrians – and Aston Martin's Arnott says he can't envisage a time when supercars will simply play their sound from speakers, nor when drivers would accept such an artifice. An authentic sound, he suggests, is so integral to the pleasure of driving a supercar, it might preclude the development of an all-electric model in the first place.

"Clearly, the sound is going to be an issue," he says. There is a worrying note to his voice. 

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