Noise cancellation in a car (active)

[Luxey]

You can guess I'm out of reality of the moment, but anyway ...

Couple of days ago I met with a friend, and blah blah, he mentioned BMW (he worked in heir Russian dealership) is offering active noise cancellation system in some models. Supposedly, it should somehow analyse environmental noise in real time, and cancel it also in real time.
Since for what I know it's impossible task, could some expert shed some light, or it's just new buzzword for white noise masking, as present in factories and workshops for decades?

[Scott Dorsey]

Luxey > wrote:
>You can guess I'm out of reality of the moment, but anyway ...
>
>Couple of days ago I met with a friend, and blah blah, he mentioned BMW (he=
> worked in heir Russian dealership) is offering active noise cancellation s=
>ystem in some models. Supposedly, it should somehow analyse environmental n=
>oise in real time, and cancel it also in real time.=20
>Since for what I know it's impossible task, could some expert shed some lig=
>ht, or it's just new buzzword for white noise masking, as present in factor=
>ies and workshops for decades?

I don't know how the BMW system works but:

1. Active noise cancellation headphones work very well. Lower frequency
active cancellation can work with speakers, as long as you don't move
your head out of the very small area of cancellation. In a car, that
may not be a problem.

2. Active cancellation _in the exhaust system_ has been tried before
experimentally and works more effectively than an ordinary damped
muffler. But it requires really big transducers and a lot of power.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On 9/23/2013 3:26 AM, Luxey wrote:
> You can guess I'm out of reality of the moment, but anyway ...
>
> Couple of days ago I met with a friend, and blah blah, he mentioned BMW (he worked in heir Russian dealership) is offering active noise cancellation system in some models. Supposedly, it should somehow analyse environmental noise in real time, and cancel it also in real time.
> Since for what I know it's impossible task, could some expert shed some light, or it's just new buzzword for white noise masking, as present in factories and workshops for decades?

As usual, this is not something new. A company called Noise Cancellation
Technogy (NCT) has been doing work in this area for at least 25 years.
One of their engineers was a friend of my local audio dealer who told me
what he heard when he was invited out there for a visit. They guy had a
box next to his desk, and a chain saw sitting on top of it. He started
up the chain saw (in his office), flipped a switch on the active noise
cancelling box, and they could carry on a normal conversation.

I've been carrying the cheap consumer version of Sennheiser's noise
cancelling headphones for years when I fly. They don't make the world go
away, but they allow me to listen to my MP3 player at a lower volume
than with the noise cancelling turned off, and I find that I'm less
tired when I get off the plane.

I have a fairly quiet car (when the tires are new, anyway) but I'd
welcome one that was even quieter.


--
"Today's production equipment is IT based and cannot be operated without
a passing knowledge of computing, although it seems that it can be
operated without a passing knowledge of audio" - John Watkinson

Drop by http://mikeriversaudio.wordpress.com now and then

[Luxey]

In small, closed enclousers, like headphones, or exaust pot (orwhatever is the word) and close placed more less point source, with more less uniform signal output, I can understand.

Like, ok, chainsaw is there, I'm here, I cancell direct on axis, enabling me to have conversation.

But in a car cabin? Ok, the main nise sources are pretty uniform (tyres and wind), but the sound comes fromm all arround, how can one possibly cancell that?
Cancelation device should be right in my head for any efficiency?