Toyota develops noise-cancelling system for carsEnlarge Photo
Like the headphones, the new Toyota system works by using small microphones to monitor surrounding sounds, then plays back frequencies mathematically calculated to be the exact opposite of the ambient noise through the speakers, causing both sound waves to collide and cancel each other out. The Toyota system has an extra sensor that takes into account engine rpm.
Debuting in the Crown Hybrid, the system was developed to cancel the annoying hum of the engine at low rpms when driving around town.
Toyota isn’t the first to develop such a system for cars. Lotus had developed similar systems as far back as 1990, and a trio of Mazda engineers having written a scholarly paper to the Society of Automotive Engineers detailing a nearly identical system in 1994. Acura, too, has a similar system dubbed Active Noise Cancellation (ANC), which it uses on a number of models.