Is there Active Noise Cancellation technology available for
residential housing to reduce noice from highway and airports?


 ( = uses the principle of destructive interference of waves to
generate an inverse pressure wave or "anti-noise" to attenuate
unwanted noise. The anti-noise is a sound pressure wave which is the
exact opposite of the offending noise: it is the mirror image signal,
exact in frequency and amplitude but 180 degrees out of phase or
"anti-phase" with the unwanted noise. In order to maximize active
noise cancellation, the canceling source always produces with great
precision an equal but inverted replica of the signal to be canceled.)
 technology available for residential housing?

This may be of interest to you:

Hobbs and Wyle Labs have also been evaluating active noise
cancellation in free space, which is considerably difficult to
achieve. Using digital signal processors (DSPs), active noise
cancellation reproduces the noise signal both in its spectrum and
amplitude, but with inverted phase. The actual noise (with normal
phase) combines with the reproduced noise (with inverted phase) and
the two cancel each other out, resulting in silence.

Hobbs typically places several microphones near the noise source to
provide a first-order phase-reversal feed to the speakers. A second
microphone is placed several hundred feet away to measure the system's
"success" and provide additional information.

"DSP-based computer modeling helps us predict what sounds are going to
do," says Hobbs. "The real difficulty is generating the acoustical
power to create noise comparable to a jet aircraft. Our expertise and
the ServoDrive BassTech 7's allow us to optimize the range of
measurement and cancellation well beyond previous capabilities."

Wyle Labs plans to implement active noise reduction systems featuring
ServoDrive BassTech 7s and SPL-td1s in various upcoming applications
as it continues its commitment to quieting our modern lifestyle.

http://www.prosoundweb.com/install/spotlight/jets.shtml

I don't think it's feasible -- active noise cancelling headphones only
need a single speaker-element for each ear.  Cancelling noise in a
large room, where the original noise is coming in through different
parts of the wall, and different windows, is a lot harder because the
source is really complex -- you can't model it as a simple wavefront. 
You need a zillion speaker elements all over the room to cancel the
noise out.

Such a problem is more demanding than recreating concert hall
acoustics using just two loudspeakers (or even 6.1 loudspeakers).  You
just can't accurately reproduce the shape of all the sound-waves
bouncing around the concert hall, when all you have is a few of
loudspeakers, and their sound is bouncing off your couches and sofas
before it reaches you.

Hi, ap12-ga:

I'm more optimistic than snsh-ga about the feasibilty of this.  When I
was a visitor at Virginia Tech some years back, prototyping was being
done on quieting of combustion engines (in cars) using ANC.  Research
has continued there:

[Vibration and Acoustics Laboratories]
http://www.val.me.vt.edu/

with some especially interesting work on active and passive "foams"
(smart skins) for noise cancellation, as well as piezoelectric based
attenuators.

For a somewhat dated review of the state of the art, see here, which
links to the above and several other sites of interest:

[Active Noise Control for the Home of the Future]
http://architecture.mit.edu/house_n/web/resources/tutorials/House_N%20Tutorial%20Active%20Noise%20Control.htm

"However, to reduce outside noises such as jet traffic or noisy street
noises ANC technology hasn't been developed nearly enough. The H
algorithm using MIMO holds the most potential. Currently, there are no
commercial/private applications of 3-D ANC scenarios in houses/offices
outside of HVAC systems. ANC works best on periodic noises (i.e.
engines). However, when dealing with a permanently standing structure,
such as a house, there is the Doppler Effect. Since the sound source
is translating the sound signal translates with the source as it is
broadcasted. This causes for a band of frequencies, and thus the
noise's pitch changes relative to a stationary point. This is what
happens if you stand by the side of the tracks and a train approaches;
it approaches as a dull rumble growing louder and louder until it
screeches (higher frequency) by you and then vanishes back into a dull
rumble. The Doppler Effect complicates the sound signal's geometry and
the complexity of the system. So as of now, this currently remains an
academic research project."


regards, mathtalk-ga

Once they had a loud outdoor festival in town, but it was next door to
a theater where they wanted it quiet inside.  Their solution was to
put huge loudspeakers outside the theater and blast white noise.  They
said it worked.

I don't know quite why it should work.  In acoustics 101 they teach
you about linearty, but maybe the white noise brings out the
non-linearities.  Maybe it dampens the resonances.

Interesting... I suspect it did not "reduce" the noise in a physical
sense, only a pyschological one.  White noise is less "distracting"
than the intermittent variations in crowd noises and musical
performances.

regards, mathtalk-ga