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Wednesday, 18 October 2006 11:26 |
 | | Carl S. Milsted, Jr. |
An organic grocery store nestled into a dense residential neighborhood ... What could be more politically correct? The food is healthy, the animals well-treated, the evil chemicals nonexistent and the customers can walk to get their groceries!
Alas, discord mars this ecotopian picture at the Greenlife Grocery here in Asheville. The neighbors are very unhappy. Delivery trucks rumble up narrow residential streets early in the morning, interrupting sleep and disturbing the peace generally.
Oh, dear! What do we do? Do we exile our grocery stores to the bypasses, forcing everyone to drive? Or do we ignore the complaints of the few nearby residents for the greater good of society?
Actually, two solutions present themselves.
The
first is legal: replace zoning with tradeable property restrictions.
Let residents own the noise and other externality restrictions on their
neighborhoods. Let businesses buy away the restrictions when they need
to make noise or generate traffic. Residents who have to put up with
noise would get paid to do so. Commercial developers would seek out
neighborhoods where people have little aversion to noise in order to
get the lowest price for noise-making rights.
The other
solution is technical: make the delivery trucks quiet. Insulation under
the hood can muffle the clicking noises from the engine. A quality
exhaust system can take out the high notes coming out of the tail pipe.
Unfortunately, it is much harder to take out the low notes from the
exhaust system ÇƒÏ the lower the note the bigger the plumbing needed to
control it. Large diesel engines put out enough low rumble to be heard
for miles, so much so that it isnët worth the bother to apply much
sound dampening elsewhere ÇƒÏ and many trucks donët.
Enter modern
electronics. Place subwoofer outputs close to the exhaust ports. Play
the same bass notes as the engine at the same volume ÇƒÏ only 180 degrees
out of phase. The two sounds cancel out. The closer the volume match
and the better the phase control, the greater the cancellation.
This technology
is easier at low frequencies than at high, since the speaker output can
be farther from the source to be cancelled. The technology is
well-developed and cheap. You can get a pair of good quality phase
canceling headphones for use on airplanes for less than $100. True, you
would need powerful subwoofers to cancel out the notes from a big
diesel engine, but I have heard many a low-income teenager with an
automobile sound system up to the task.
With the low
notes dealt with, it becomes worthwhile to apply conventional
techniques to muffle the higher notes. But we still have an annoying
noise thatës required by law: the loud beeps emitted when the truck is
in reverse.
I could argue
that this beep could be quieter if the truck as a whole is made
quieter, but I might be wrong: trucks often operate in noisy
environments. Conceding this point, I think that it would be safe to
limit the high volume beep to the danger zone: the blind spot behind
the truck.
The technology
to focus high pitch beeps is straightforward. Instead of having a
single high-powered tweeter to emit the beeps, place a linear array of
lower power tweeters across the back of the trailer. In the driverës
blind spot, the power of these tweeters will add up. Off to the side,
the output of the tweeters will be out of phase, canceling out much of
the sound. The result is a beam of sound focused where it is needed.
Perhaps we
should apply the same principle to train whistles as well, focusing the
sound to those ahead of the train. And maybe we should demand phase
cancellation on semi trucks in general, opening up land closer to the
highways for peaceful living.
The result would
be a more pleasant urban environment, leading to less suburban sprawl ǃÓ
and more opportunities to open an organic grocery store in a dense
residential environment ....
ï
Carl S. Milsted Jr. is chairman of the Libertarian Party of Buncombe County.
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