Background

Customer demand and a competitive market have led manufacturers to strive for ever greater levels of refinement in their vehicles. Increasing use of lightweight structures and green technologies, coupled with a greater emphasis on vehicle dynamics means that it is often difficult to achieve NVH targets using conventional passive techniques alone. In addition, stringent exterior noise legislation and increasing use of platform sharing has diluted the distinctive brand character of many vehicles.

To address these issues, Lotus has developed a suite of Noise Management Solutions that together target 4 major NVH attributes of the vehicle – Engine Order Cancellation (EOC), Road Noise Cancellation (RNC), Internal Electronic Sound Synthesis (IESS) and External Electronic Sound Synthesis (EESS).   

Engine Order Cancellation (EOC)

The Lotus EOC system targets the low frequency tonal (booming) noise associated with harmonics of engine rotation. The system employs an adaptive controller to cancel engine order related noise using the standard in-car entertainment loudspeakers in the vehicle. An engine speed signal is used to provide the controller with a frequency reference, whilst error microphones are used to continually optimise the cancellation.

Key benefits of EOC

•    Typical reductions of 10dB or more in 2nd order noise at all seats (global cancellation)
•    Simultaneous cancellation of multiple engine orders within frequency limits
•    Cancellation of intake and exhaust noise is also possible
•    No restrictions on engine type (petrol / diesel) or configuration
•    The system can be used to control active engine mounts or active seismic absorbers
•    The system can be integrated with the existing vehicle audio system and with Lotus Road Noise Cancellation / Sound Synthesis
•    Cost & weight savings through deletion of passive NVH materials
•    Reductions in engine weight, cost and power consumption through the deletion of balancer shafts

Road Noise Cancellation (RNC)

Lotus RNC targets the low frequency, broadband rumble associated with road noise. The system uses accelerometers on the vehicle to provide a reference for an adaptive controller, which cancels the structure-borne component of the road noise using the standard in-car entertainment loudspeakers. Error microphones are used to continually adapt the cancellation.

Key Benefits of RNC

•    Typical reductions of 8 -12 dB in low frequency road noise at all seats
•    The system can also cancel the effects of structure-borne powertrain noise (for example idle booms)
•    The system is fully adaptive and the cancellation is continuously optimised
•    The system can respond to a change in road surface in less than 0.25s
•    The system can be integrated with the existing vehicle audio system and Lotus Engine Order Cancellation / Sound Synthesis
•    Reductions in driver fatigue associated with exposure to low frequency noise
•    Improved fuel consumption due to lower vehicle weight

<!--[if !vml]--><!--[endif]-->Internal Electronic Sound Synthesis (IESS)

Sound quality is an important factor in communicating brand values - customers expect sound quality to match brand image, however stricter exterior noise legislation is diluting engine character. The Lotus Sound Synthesis system enhances interior sound quality by introducing additional engine orders using the standard in-car entertainment loudspeakers. The output of the system is a function of both the engine speed and throttle position.

Key Benefits of IESS

•    The system can be used to create a more sporty or sophisticated sound
•    External noise remains the same - no modifications to the intake or exhaust are required
•    The system can be integrated with the existing vehicle audio system and Lotus ARNC / EOC