New software helps deliver more silent drives

Several features make luxury cars different from standard vehicles, including more powerful engine, more legroom in the back, smarter on-board computers, and a smooth, silent ride.

Thanks to a new piece of software the last feature may get an enhancement. The new software helps cancel noise generated from hitting unpredictable bumps in the road to make for a more silent ride.

Designers have traditionally used "passive" noise-reduction methods that rely on the use of materials in the body of the car to absorb sound waves as they are produced. The method gives the best results with higher-pitched noise, like the screeching of brakes. However, the cancelled frequencies are limited with deeper, more irregular sounds getting through.

Active noise-control (ANC) systems detect the car's noise as it is generated and then produce a sound wave that is out of phase with the original. The peaks of the generated wave match up with the troughs of the original, with the two cancelling out. The original sound has to be quickly through on-board computers, so that a cancelling wave can be sent to intercept it.

An algorithm developed by Guohua Sun and colleagues, at the University of Cincinnati in Ohio, takes this a step further, adapting to and cancelling noises that are not regular or predictable. Existing ANC systems are designed on the assumption that all noise from the contact between car and road will follow a pattern, which works pretty well for the regular thrum of tyre on tarmac. However, when a car hits a bump in the road, the conventional algorithm fails and the noise gets through much to the driver's discomfiture.

The University of Cincinnati team's algorithm can handle these sound spikes. It calculates a cancelling sound wave for irregular and unexpected noises. In a numerical model, the system worked better than standard ANC, and according to Sun, a real reduction of 50 per cent would be see when the system is tried in Ford cars next year.