Software helps cars go quietly over bumpy roads

A host of features separate luxury cars from the standard vehicles most of us drive: a more powerful engine, more legroom in the back, smarter on-board computers, and a smooth, silent ride.
That last perk may be about to get an upgrade, courtesy of a new piece of software that can cancel noise generated from hitting unpredictable bumps in the road.
Traditional "passive" noise-reduction methods rely on using materials in the body of the car to absorb sound waves as they are produced. This method works best with higher-pitched noise, like the screeching of brakes. But the frequencies they cancel are limited; deeper, more irregular sounds tend to get through.
Active noise-control (ANC) systems listen to the noise being generated by a car, 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, and the two cancel out. The original sound must be analysed quickly through on-board computers, so that a cancelling wave can be sent to intercept it.
Guohua Sun at the University of Cincinnati in Ohio and colleagues have developed an algorithm that take this a step further, adapting to and cancelling noises that are not regular or predictable. Existing ANC systems rely on the assumption that all noise from the contact between car and road will follow a pattern. This works for the regular thrum of tyre on tarmac. But when a car hits a bump in the road, the conventional algorithm breaks down, and the noise gets through to rattle the driver's ears.
The team's algorithm can handle these sound spikes, letting it calculate a cancelling sound wave for irregular and unexpected noises. In a numerical model, it outperformed standard ANC, and Sun says he expects to see a real reduction in sound of at least 50 per cent when the system is trialled in Ford cars next year.