🚀 go-pugleaf

A few weeks ago we had someone here say that dynamic sound/noise
reduction required some microphones and a digital signal processor then
the signal was inverted 180 degrees to oppose the originating noise.

My question is: why the digital signal processor?

The reason for my question is:

I would like to build a system that would reduce the noise that
arrives at my home from a highway that is about 1/2 mile away.

My idea would be to get two microphones one loudspeaker and some
circuits.

The first mic (A) would be about 40ft from my house and the second mic
(B) would be about 20ft from my house and they would both be in-line
from the highway noise.

The first mic's signal would be fed through a delay line of about 40
milli seconds (thats the time I figured it would take the sound to get
20ft from mic#1 to mic#2) and produce signal A'.

The loudspeaker would be in the direction of the house and located near
mic#2, and connected so that the signal would be 180 degrees from the
incoming highway noise.

A' = delayed signal
B  = signal from second mic
C  = intermediate signal (calculated)
D  = fed to loudspeaker in the direction of the house to
     cancel out the highway noise

The circuits would do the following analog calculations:

A'-B=C
B-C=D


Is this possible or am I missing something?

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