As a student of audio recording, I subscribe to a site called Audio Masterclass. I read an article today that I thought would be helpful to my readers. It covers the basics of how to achieve better acoustics in your studio. Read on...
A brief
introduction to acoustic treatment for the home recording studio
When you
have achieved good soundproofing in your room, you will need acoustic
treatment to make it sound good both for recording and monitoring.
By David
Mellor, Course Director of Audio Masterclass
Acoustic treatment and soundproofing
are two totally separate concepts. To start thinking about acoustic
treatment, imagine a room constructed from thick concrete - walls,
floor and ceiling. It's soundproof, but it sounds terrible because of
the strong reflections from the hard, parallel surfaces. So let us
consider how we would apply basic acoustic treatment to this room...
Acoustic treatment should achieve one
of two things. Either it should make the room sound pleasant, or it
should make it as dead as possible. Sounding pleasant is best, but it
is difficult to achieve in small rooms. In a small room, such as the
smallest bedroom of your apartment or house that you want to convert
to a studio, it is often more practical just to deaden it as much as
possible. The reason for this has to do with the frequencies of the
standing waves that are created in small rooms, but that's a more
advanced topic for another occasion.
Suppose though that you have a fairly
large room, around twenty square meters or more. It's still made of
concrete remember. What you want to do is get rid of the ugly
reflections and replace them with a pleasant acoustic ambience in
which to make music.
What the bare room has is a small
number of very strong reflections. Small number - very strong. This
is important. So firstly you would need to consider absorbing some of
the reflected sound. This can be achieved in two principle ways...
Porous absorbers
It's easier to give examples of
porous absorbers than to embark on a long-winded scientific
description. Carpets, curtains and cushions are all great porous
absorbers. The "Three C's" of acoustic treatment perhaps.
But there's a cheaper material that makes an excellent porous
absorber - mineral wool. You will find this at a builders' merchant
in the form of loft insulation. It's intended for thermal insulation,
but it works extremely well for absorbing sound too. Fiber glass loft
insulation can work too, but mineral wool is more commonly used
professionally. The only downside of mineral wool is that it sheds
fibers and must be contained behind a fabric barrier. But you would
want to do this to make it look good anyway.
Porous absorption is great, but it
has one limitation - it only works well at medium and high
frequencies. To work well at low frequencies it has to be VERY thick,
or spaced away from the wall. A room that is treated only with porous
absorption will be dead at high frequencies but still reverberant at
low frequencies. Subjectively the room can sound rather oppressive,
to the point of not being a pleasant place in which to work. Having
said that, a room that has only porous absorption will be better than
a room that has no absorption at all. Those bare concrete walls,
remember?
Panel and membrane absorbers
Panel and membrane absorbers are
basically the same thing, but the way in which the terms are commonly
used changes according to the nature of the material used.
What we would normally call a panel
absorber is a wooden panel mounted on a frame that spaces it away
from a wall. The space behind the panel is completely enclosed. Sound
energy is absorbed in the meshing of the wood fibers as the panel
vibrates in response to sound. The panel absorber can be tuned to a
specific range of frequencies, according to a formula that includes
the mass of the panel and the spacing distance. It is perfectly
practical to tune panel absorbers to work well at low frequencies,
where porous absorbers struggle.
What we would normally call a
membrane absorber uses a flexible surface, such as a material with a
rubbery consistency. Where a hard panel will reflect some sound
energy and mid and high frequencies, the flexible membrane will
provide absorption in itself, regardless of the air-space behind. It
too can be tuned, but the panel absorber is more precisely tunable to
specific problem frequencies.
Diffusion
Absorption isn't the whole of the
story in acoustic treatment. Going back to the bare concrete room
with just a few strong reflections. These will occur at certain
frequencies dependent on the dimensions of the room. Having just a
few strong reflections, creating resonances at certain frequencies,
is subjectively unpleasant to the ear. It is much better to have many
weak reflections, which will create a diffused sound field within the
room.
This can be done with hard, irregular
surfaces. You can buy diffusers, or make them yourself. A bookshelf
filled with books of different sizes actually works quite well and
provides a combination of diffusion and absorption.
In summary, good acoustic treatment
consists of a combination of porous absorption, panel/membrane
absorption, and diffusion. Although the very best results will be
achieved through scientific methods and calculations, surprisingly
good results can be achieved through educated guesswork and
experimentation.
One more point...
Although professional recording
studios have separate recording rooms and control rooms, at Audio
Masterclass we recognize that most home recording studios have just a
single room. Ideally the requirements in terms of acoustic treatment
are different for recording and for monitoring, but there are methods
and techniques that can be used to get the best results according to
individual circumstances.
 |
David MellorCourse
Director, Audio Masterclass
Wednesday, January 1, 2014 |
P.S. I have personally been dedicated
to Audio Education since 1986. Audio Masterclass has been online
since 2001. We have helped literally thousands of our enrolled
students make better recordings.
(end of article)
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