17th January 2005

LOTUS TECHNOLOGY COMBATS LOUDER INTERIOR OF THE MODERN CAR

As it launches a new patented system for actively tailoring vehicle acoustics, British automotive consultancy Lotus Engineering has found that many new cars subject their passengers to higher internal noise levels than their predecessors.

The surprising findings apply particularly to high volume family hatchbacks and superminis. Modern cars are undoubtedly better value for money, better equipped, more reliable, more fun to drive, more fuel efficient, and are safer. But as the issue of increasing interior noise is confounding the automotive industry, Lotus is launching a technology to solve the problem.

The Hethel-based consultancy's 'In-Car Active Acoustic Tailoring' (ICAAT) system allows vehicle manufacturers to create an acoustic ambience that matches consumers' expectations, and which can even be tailored to suit individual driving styles and auditory expectations.

"It's a surprise to most people that while you'd expect every aspect of a car to have improved over the last ten years, noise levels inside the car have actually worsened in the majority of cases," reveals Steve Swift, Head of Vehicle Engineering at Lotus. "As the number of clients requesting our help in this area has increased, we've been working to refine our active noise solution. With the newest version, ICAAT, car manufacturers can discreetly improve and manage interior noise characteristics."

Lotus has observed that over the last decade, while engine noise and wind noise have decreased, the efforts of manufacturers to make cars more attractive, safer, and more fun to drive have resulted in greater in-car noise.

To improve the appearance of today's cars, manufacturers fit larger wheels, alloy not steel, and low profile, wider tyres, more frequently of a run-flat design for increased safety. These welcome improvements may enhance styling and safety, but produce greater levels of road noise and transmit more of that generated noise to the passenger cabin.

The suspension configuration of modern cars compounds the issue. A decade ago, most hatchbacks had standard beam axle suspension, but many modern hatchbacks now feature multi-link suspension as manufacturers pursue superior ride and handling. This setup, however, offers multiple paths for vibration and noise to enter the car.

The noise is not only an annoyance, but according to Swedish researchers the presence of a low frequency monotonous noise can make drivers feel drowsy, which is widely believed to be a factor in some accidents.

Low frequency road noise cannot be effectively treated with conventional NVH tools without compromising vehicle dynamics performance. Lotus is marketing ICAAT as a viable and cost-effective solution, integrating road noise cancellation and engine order cancellation.

ICAAT works by reducing unwanted noise in the relevant frequency range from both the road and engine. Through complex algorithms, the technology then generates sound of an opposing phase through the car's standard speakers, suppressing the perceived level of noise for passengers.

In addition to eliminating unwanted engine and road noise, ICAAT also features a sound generation mode, as Swift explains. "ICAAT is capable of producing engine sound cues as well as suppressing unwanted noise.
Manufacturers could therefore tune the engine tone characteristics between different models in a product range. Alternatively, there is the option to leave the decision to individual drivers, allowing them to choose the engine tone dependent on their mood or preferred driving experience. It's an extremely versatile and valuable technology."

Lotus' first generation active engine noise suppression system was fitted to Japanese-specification Nissan cars in the early 1990's. ICAAT builds on the performance of Lotus' previous active technology, but is significantly lower cost, and integrates into a single system the functionality of engine order and road noise cancellation, in addition to the sound synthesis feature.
Increased performance and lower cost means that active acoustics are now, more than ever, a commercially feasible proposition for high volume vehicle manufacturers. As a result the first version of the new technology is already in demonstrator vehicles, and the Hethel-based consultancy is now in advanced stages of discussions with OEMs and Tier-One ICE suppliers regarding mass-production of ICAAT.