Seeking to eliminate concerns about the potential threat that near-silent hybrid could pose to unwary pedestrians or cyclists, Lotus Engineering has developed a system that creates realistic engine sounds to warn of people of their proximity. Long a preeminent force in the realm of active noise cancellation technology for passenger cars, Lotus holds numerous patents in the areas of Active Road Noise Cancellation, Engine Order Cancellation and Sound Synthesis, which form the core disciplines of its expertise. Its new Safe & Sound Hybrid technology expands on the Sound Synthesis aspect of firm's knowledge base, but here, it's used to modify the vehicle's sonic signature outside rather than inside of the passenger compartment.
Centerpiece of the Safe & Sound Hybrid system is a synthesized digital sound sample of a representative conventional engine, which is drawn from its entire operating range to insure the proper pitch and frequency characteristics. At the moment the vehicle switches over to electric power, a waterproof speaker at the front of the car begins projecting an appropriate audio "voice" forward that reflects operating input data it receives from a controller linked to the accelerator pedal. As soon as the car's internal combustion engine restarts, this electronic counterpart automatically ceases in a seamless process that the driver and passengers are virtually unaware of. Although Lotus demonstrated its new Safe & Sound Hybrid system on a standard Toyota Prius, a variation on the basic concept has potential for application on pure electrics as well.