# Is active noise cancellation useful in vehicles?

The cabin noise of vehicles is a large concern in the luxury market. Why haven't any automakers used the same techniques as are employed in active noise cancelling headphones. In these devices a microphone is used as an in-loop sensor to suppress low frequency ($f\lt500\ \text{Hz}$) pressure fluctuations in the enclosed space near the ear.

Why isn't similar technology used in vehicles? What technical improvements are required over the standard vehicle sound system to implement it? Given the increased volume of the system, what differences can be expected between vehicles and headphones?

• I'd guess there are safety concerns. Noise canceling headphones reduce sound in those frequency ranges indiscriminately; emergency sirens and other sounds you need to hear while driving won't be as audible. Also, human voices are <500Hz and there might be the potential for not being able to talk to your passengers (not always a bad thing) (also I'm not sure that's how noise-canceling works, just a thought.) Jan 30, 2015 at 18:45
• Looks like this are already in use in some production cars.
– Dan
Jan 30, 2015 at 19:02
• Only a few days after posting this question I saw a car commercial which advertised active noise cancellation (I can't remember which brand though) :) Feb 9, 2015 at 23:12
• @TrevorArchibald many of the same safety concerns were brought up when Toyota first started selling Lexus cars here in 1989/90. Compared to almost all other passenger vehicles, the LS400 was amazingly quiet and isolating. Nov 30, 2015 at 20:25

Some reasons why noise reduction in vehicle cabins is not a standard feature, yet:

• As @Trevor Archibald states, safety is a very good reason. There is still a need to hear some noises from outside the vehicle such as the sirens of emergency vehicles: police, ambulance, fire fighters truck
• Hearing car horns from other drivers is still needed
• The sound of the engine lets people know if the engine is performing as it should
• It's an added cost some people may not want to pay
• People haven't asked for it
• Most people don't object to hearing some noise, as long as it's not intrusive
• Insulating vehicle cabins against noise by using sound proofing materials has suited most peoples needs until now

It has been introduced in a small number of cars: Auto Makers Shush Cars, but these are a bit more expensive than the average car. See also: Cars Go Quiet, Bose Noise Cancelling in Cars

However, introducing electronic noise reduction technology in cars, could reduce the weight of cars by reducing the amount of sound proofing materials used, Harman Quiets the Car

On a different angle, in the 1980s electronic noise cancelling had been used to cancel the engine noise made by heavy vehicles used in inner urban development site to reduce the amount of noise heard by nearby residents.

• This is written from a consumer point of view but I took the question more about an engineering point of view, kind of: would it technically be feasible? Basically, how well does it work in cars? Feb 4, 2015 at 9:39
• The fact that the technology has already been introduced in some cars & there are plans to introduce into some lower priced models & hybrids means it is technically feasible. The fact that something hasn't been introduced doesn't mean it's not feasible. Economics is a big factor: are people prepared to pay to have it in cars they use. Besides it's not critical technology, not like good brakes, an efficient motor, safe fuel tanks that wont rupture in a crash. It's a "nice to have" technology. Safety & client needs are a big part of engineering.
– Fred
Feb 4, 2015 at 11:18