Sounds are back by popular demand - and car-makers are making cars noisier
The preferences of drivers for the sound of their cars is almost as diverse as their music favourites. Some like the hot sound of a sports car, others the dulcet tones of a luxury limousine, while still more hanker after a rally rocker.
But, with the constant push for ever more refinement in even basic cars, things have now reached the stage where an increasing percentage of car buyers are complaining that their motors sound boring. So the engineers are dialling back in the sounds that seem to be required by various target buyer groups.
When a humble Toyota Yaris is seen as being as well built as a Mercedes, it is the perceived things that make the kind of difference manufacturers can charge for.
So, in many cases, they're removing the silence that they've put so much effort into achieving. Or more accurately, manipulating the acoustic environment to provide a very carefully created audial experience.
It's all a far cry from when young motorists opened out the baffles in their exhaust system to recreate the loud crackle of racing and rally saloons. Which, of course, young drivers still do, even if the result is actually less power because they've mucked up the carefully-designed systems. It's the noise, guys.
It's also a quite selective process, with car-makers researching and plotting the kind of feedback sounds that appeal to their particular target buyership for any particular model.
Lexus is the example at one end of this. The brand's first car, the LS 400, was deliberately designed to be as quiet as possible, because that was the perceived requirement of the upper luxury buyers in its key market of the US.
At the other end of the sonic rainbow, the Mercedes-McLaren emphasises the raw power of its engine in a way that was superbly described, by Gavin Conway of the Channel 4 Cars programme, as "a bellowing thug, a vicious jackhammer under full throttle, all of it overlaid with the piercing scream of the supercharger".
To the Lexus LS owner, this must sound like a description of motoring hell, but the Mercedes-McLaren driver would probably be bored to witlessness after a day in the Lexus.
BMW is at it too. When the company was developing its Z4 sports car, its 100-strong team of acoustic engineers were charged with designing an engine sound management system that deliberately feeds a carefully blended mix of sounds back into the cabin. On the other hand, its top-level 7 Series saloons can be so quiet that at idle it's hard to know if the engine is running.
And Alfa Romeo, of which aficionados make much of the Alfa "song", puts much thought into tweaking its current GM-sourced petrol engines so that they provide similar arias. The same base engines in European and Australian GM applications sound completely different.
Jaguar and Land Rover now use the same basic V8 petrol engines, but they can make them sound different in the two brands.
Local regulations also have to be taken into account. Listen to a Ducati motorbike in its native Italy, for instance, and it sounds great. The same bike as sold in Germany, which is much more strict about drive-by sound levels, is a much quieter machine, and not at all as interesting.
Sussing out the right sound is almost more an art than a science, and can be analogous to an experienced whiskey blender producing a particular end taste from a variety of individual whiskies.
Peel, for instance, has a sound studio where it holds acoustic "concerts" of engine sounds. "We let people listen to the sounds and ask them what they prefer," says Helmut Huskier, one of the company's sound specialists. "Then we work on reproducing those sounds. You can't do it all on a computer - you need very experienced people who drive cars under different conditions and who can tell you what you have to do."
And, like the guy who blends the whiskey, the results have to satisfy the not very experienced people as well as the purists.
Ford has a sound quality laboratory where it tries to discover its customers' likes and dislikes when it comes to a car's total acoustic environment. Among other things, the lab analyses engine noise, which is a result of a number of different inputs, some predictable, others random.
The predictable ones include pressure pulses produced by the burning of fuel in the cylinders, and can vary widely depending on whether the engine is 2-stroke, 4-stroke, a "straight" or "V" configuration or the so-called "Boxer" opposed-cylinder format as used by Porsche and Unbar. There's also the unique sound produced by the rotary engines of Mazda's RX8.
Even the kind of "V" format makes a difference. The much-loved burble of a typical American V8 comes about because they have a 180-degree angle between the cranks. A Ferrari racing-type V8, with a 90-degree crank angle, doesn't have the burble.
Random noise comes mainly from the turbulent air flow in intake and exhaust systems, as well as from accessories such as engine cooling and alternator fans.
It all makes for an extraordinarily varied set of ingredients, from which a wide range of audial "cakes" can be baked. In a demonstration of its Active Noise Control technology, Siemens DO recently showed both its products and the results of research which aimed to set down just how control of engine sound can significantly influence drivers' enjoyment and comfort levels.
The company's trials indicate that the tastes of drivers can change with their location, driving conditions, and even time of day. It seems drivers like their engine to be quiet during bad weather or at night, while in city traffic they want harmonics that accentuate acceleration phases.
The company's technology uses a microphone in the air intake system to monitor and measure sound levels at particular driving situations. Then a corresponding tone sequence is delivered into the intake system by a speaker, so that the resultant noise inside the car is one known to be popular.
Project manager Dr Marcus Lewis says that low and constant sound levels are not as popular as harmonious sequences of tones. He said that motorists make similarly high demands of a good engine sound as they do on a music symphony.
The sentiment is echoed by Peel's Huskier, who notes that the choice of resonators used in tuning the sound from engines is based on pleasurable frequencies and sequences produced by musical instruments.
"To my knowledge, the music used is European classical, and there are a lot of parallels between instruments and engine sound. As for other cultures such as India or China, where the musical systems are different, I don't know . . . but I can only suggest that in those emerging markets expectations are more for reliability than for sounds that they would consider pleasant."
Maybe, not so far down the road, a driver will be able to dial a sound into their engine that reflects their musical preferences. So we could have the "Bono burble" or the Chopin canto" - even the "Eminem mutter"? But there'll still be fellas out there preferring their big-bore blown baffle thunder. That'll be the Geldof grunt . . .