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
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
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
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
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
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
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.