Recording - November 2015 - 24

I have a deep love and respect for
mythology (Norse is my current favorite).
While the myths and stories of our ancestors may not be an abundant source for scientific truth, they are packed with meaning
that can inspire us and enrich our lives.
This kind of meaning is what drives art in
general, and without artistic meaning,
what's the point of recording music?
As a result, I'm not a big fan of "mythbusting" or "debunking". Implied in these
terms are absolutes that I rarely agree with:
that the "myth" (taken as a synonym for "lie")
being "debunked" has no truth to it whatsoever, and that anyone who "believes" in it is
therefore ignorant and/or stupid.
On the contrary, I find that many of
these "myths" have their roots in truth.
More often, the problems tend to come
when the truths are misinterpreted or
taken to an extreme that isn't always the
most accurate way to think about the
problem at hand. Like all mythologies,
audio myths are an invitation to think
more deeply about a given scenario.
Furthermore, acoustics is one of the
most counterintuitive sciences out there. So
many things in acoustics just don't make
sense at first glance, and once you dig in,
turn out to not be as they appear. Though
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RECORDING November 2015

the situation is much better now than it
was 10-15 years ago, when we saw a lot
of egg cartons stapled to walls in music
rooms for "acoustic treatment," there
remain some commonly-repeated ideas
circulating in the audiogeek-o-sphere that
aren't the most accurate interpretations.
I'd like to address some of the most
common ideas I encounter in my day-today work as an acoustics consultant,
where I help people improve the sound of
their rooms. I'll try to find the germ of truth
within the myth and show how we can
benefit from better understanding.
1. Parallel walls are bad
This is perhaps the most common example of "rooted in fact but taken to misleading extremes". The argument goes
something like this: parallel walls cause
standing waves, which will wreak havoc
on your bass response in the room.
The fact is, all rooms have standing
waves, whether there are parallel surfaces
or not. And furthermore, standing waves
are only one manifestation of acoustics
problems that occur in rooms. In other
words, even if we could completely eliminate standing waves from a room, there
would still be acoustics problems to address.

Here's the truth in this idea: parallel
walls cause flutter echo. Flutter echo is
definitely a problem; it sounds almost like
a metallic "boinging" sound. If you have
a staircase that is finished in drywall, it's
easy to hear extreme flutter echo by
going into it and clapping your hands.
Luckily, flutter echo is one of the easiest
acoustics problems to solve. It can be done
with absorption or diffusion. Even a thick
blanket put across one of the parallel surfaces will improve or solve flutter echo. In
fact, this is a great way to test and see
where it is coming from, since it can be
applied temporarily as a test (either with
duct tape, or by draping the blanket over
a mic stand set up in a T shape). Real
acoustic panels, either broadband
absorbers or diffusors, work even better.
But rooms with parallel walls have a
plus side! They are very predictable
acoustically, they are relatively easy to
treat, and they are simpler (which usually
means cheaper) to construct. In fact, if I
wanted to build an audio room to maximize cost-effectiveness, then I would build
a rectangular room, taking up as much of
the available space as possible (such as in
a garage or a basement), and make sure
that no two dimensions of the room are

Table of Contents for the Digital Edition of Recording - November 2015