From Acura to VW, BMW to Porsche, Car Companies Are Getting Sneakier About Engine Sound Enhancement
Automakers are doing whatever it takes to give their cars' engines some added acoustic zing.
Over the last decade, auto manufacturers have been engaged in a silent war against, of all things, quietness. Ordinarily, quiet is a desirable quality in cars—engineers actively battle wind roar, tire drone, and vehicle vibration in every new product—but a little bit of noise in the right place, like a crackly, roaring exhaust notes to complement spirited driving, can transform the driving experience. Naturally mellifluous engine noise, however, is fading with the times. Improved sound deadening and ever-more-efficient (and smaller) engines have made it harder for engines to cough up anything better than a muted turbo whine. That’s great for drivers who enjoy peaceful commutes—but many buyers, particularly of performance machines, still thrill to the sound of a great engine.
To fix this, car companies have begun taking extreme measures that, over the last few years, have morphed into routine ones...though they're rarely touted, and only reluctantly discussed.
Early this decade, Volkswagen Group installed a little black disk called a soundaktor, or sound actuator, at the base of the windshield to vibrate the glass in sync with the engine, injecting computer-generated noise to accompany the natural engine note. When enthusiast owners got wind of this, many disabled or removed the device, feeling it was inauthentic. (They instead opted for aftermarket exhausts, which can generate significant rumbles from even the smallest engines.) But VW persisted with this strategy—and in fact, has doubled down on it since then, spreading the digital trickery to Audi’s performance lineup, including the A5, S5, and RS 5 coupes, the S4 sedan, the TT and TTS sports cars, and the new RS 5 Sportback.
BMW has used an even more controversial system for several years now. First introduced in the previous-generation M5 in 2012, Active Sound Design delivers recorded engine noises through the car’s stereo speakers, synced up with engine speed and other variables. The goal is not just to make the car fun to ride in—it can make a four-cylinder engine sound like a beefy six—but also to help drivers shifting manually better gauge when to change gears, as even high-revving engine noise can now vanish at higher speeds. A company spokesman confirmed the system continues to spread throughout the BMW lineup, and is now found in certain 3, 4, and 5 Series cars, most of the performance-enhanced M models, the i8 hybrid sports car—which uses it most notably to help jack up the aggressiveness of its modest three-cylinder engine that charges the car’s battery—and the X3 M40i, X4 M40i, and X6 50i SUVs.
Porsche has also been eager to maintain its acoustic edge, not surprisingly, but it has done so through more natural mechanisms, including a sound symposer that uses a plastic hose to pipe engine noise into the cockpit—though with a membrane that blocks gas fumes, of course. The system is activated in Sport mode, when a small flap opens up to send the eardrum-pleasing audio up to the occupants. According the company, having a degree of engine noise enhancement isn’t just an experience issue, but also a performance one, as it better links driver to the machine by helping them gauge engine speed and strain.
Ford and General Motors use a similar stereo-based system to enhance their more muscle-bound products, including FoMoCo's F-150 and Mustang and the Cadillac CT6, CTS, and ATS models. Indeed, Cadillac has been working to push the capabilities even further, incorporating Bose noise-cancellation technology into the cars that offer the Bose premium sound systems. The idea is to fine-tune the interior experience by dialing out the unwanted noises—like road noise—while puffing up the more-desirable sounds.
Acura is equally aggressive in this respect. The company’s products now carry an Active Noise Cancellation system that reduces low-frequency noises generated by the road surface; it uses overhead microphones in the cabin to generate a “reverse phase” audio signal through a special amplifier, which then cancels out the original noise using the doors speakers. A complementary system called Active Sound Control then steps in adjusts the sound pressure levels from the engine and improve the engine’s acoustic signature while inside the cabin. According to a company brief, “engine noise doesn't increase in a linear way with rising revs; instead there can be many resonances that create peaks and valleys in the sound pressure level and an uneven sound.”
The ASC system creates a same-phase or reverse-phase sound signal as needed through the car’s speakers to adjust the sound pressure—even when the stereo is turned off. It makes the largest difference in the range between 1,400–2,400 rpm for V-6 engines, and 1,000–1,800 rpm for four-cylinder motors. The system is also tuned based on drive mode and trim level, including a louder engine noise in the company’s A-Spec models, where it increases engine noise in the cabin by up to four decibels. A company spokesman confirms the system is standard on the ILX, TLX, RLX, and MDX, as well as the NSX supercar. (The company’s parent brand, Honda, only puts it in the 2018 Accord.)
So even while automotive purists might balk at the practice of boosting engine noise, it’s clearly here to stay. This is particularly true given that stricter sound and emissions controls—at least in Europe—are further tightening the noose on engine noise. Of course, the carmakers might at some point take a cue from the electric vehicle market. Those machines, which in the U.S. will be required by 2019 to emit audible noises to alert pedestrians to their presence, nevertheless will likely maintain whisper-quiet interiors, augmented solely by the occasional motor whine under aggressive acceleration and the increasingly muted wind and road noise. It’s a quality that EV enthusiasts tend to love—even in performance variants such as the Tesla Model 3 Performance and the Model S P100D. On the other hand, that argument hasn’t swayed many of the exhaust-note enthusiasts so far...and it probably won’t any time soon.
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