At least one car manufacturer (GMC) advertises a “noise cancelling” system available in new model trucks. Bose also claims this feature for their headphones.

Exactly what is “noise cancellation.” Is there something aftermarket we can install in our Z cars?

 

It's another tech feature that only OEMs can afford to engineer into specific models. They use sound waves generated by speakers to cancel out noises that are deemed unpleasant. That would be difficult to engineer into an aftermarket unit that could go into hundreds of cars.

 

The system was originally developed by Lotus Cars, which GM bought a few decades back, and is now finally being put to use. There's a mic inside the cabin as well as a speaker(s). The mic pics up the ambient noise and its wave pattern is inverted and sent through the speakers. Simple math (-1) + (+1) = 0, so the inverted sound wave cancels the original. Noise-canceling headphones work the same way.

 

The stock BOSE system has this, its called Audio Pilot... and I think its one of the many reason the BOSE system sounds so bad. The technology wasn't that good back in 2003 when the car came out.

As dcains mentioned the theory is simple: a microphone picks up background sounds and plays the opposite sound thru the speakers thus cancelling out the original background sound. I have BOSE's noise cancelling headphones and they work great on airplanes. They almost completely kill that droning sound of the jet engines.

There are some aftermarket DSP systems that will do the same thing.