When you record an instrument in a space,
you’re capturing the direct sound of the
instrument and the ambient sound of the space
itself. The balance of room sound and direct
instrument sound depends on many factors,
including how near the mics are to the
instrument, the pickup patterns of the mics and
the volume level of the instrument. However,
one thing that remains constant is the acoustic
character of the particular space, and most
people can hear the difference between a large
space such as a concert hall and a small space
such as a domestic lounge.
In simple terms, we can view this acoustic
effect as having two components: early
reflections and reverberant decay, or ‘tail’. The
latter tends to be quieter and comparatively
diffuse, whereas early reflections tend to be
more defined and clearly indicate the size of the
space. Even in a domestic setting, these
differences can be quite marked, from the
clattery sound of a tiled bathroom, to the
reverberant nature of a hallway, or the almost
dead sound of a soft furnished space.
The sound of each room is a function of its
size, shape and contents, particularly whatever’s
on the walls, ceiling and floor. When recording,
it’s important to tune in to this and use it to your
advantage if possible. For that reason, if you’re
recording in a domestic environment, rather
than spending time and money trying to design
an acoustic space from scratch, it might be
simpler to just use a room that closely
approximates the sound you want. Although
this may not be particularly convenient and
raises issues of isolation (see below), it can often
yield the best results.
Whichever space you choose, it is possible to
change the acoustic quite dramatically through
various means. Typically, the more empty the
space, the more ‘live’ it will sound, so to deaden
a room you need to put more stuff in it.
Upholstery and soft furnishings are very
effective, and carpets and curtains in particular
change a room’s character noticeably.
Conversely, if you want to liven up a space,
add reflective surfaces. The floor is often the
nearest surface to the instrument being
recorded, so if it’s carpeted, placing a
wooden sheet on top can liven things up.
Opening curtains and revealing any glass
surfaces can also be helpful.
Isolation
Isolation is one of the hardest things
to achieve in a recording environment
and takes in a number of
considerations. First, it’s important to
try to isolate the space we’re
recording in from outside noise,
especially if you’re recording a quiet
source instrument, or one with a long
sustain/decay. It should come as no
surprise that professional recording
spaces go to great lengths in this
department, building floating rooms
inside rooms, with dual layer doors and large air
gaps between window glass. In a domestic or
project environment, however, we need to be a
bit more realistic, looking at the specific things
we can control and those we can’t.
Making sure doors are closed and windows
are sealed is obvious, and goes a long way to
keeping out mid- and high-frequency sounds –
birdsong, sirens and so on. Distance also helps: if
your neighbour likes to turn up the bass, getting
as far away from the party wall as possible will
help. And although in theory the attic is a great
place to stick your studio, if it rains or gets overly
windy, you’ll be able to hear it through the roof.
The next type of isolation concerns the
sounds you make and how bothersome they are
to your neighbours. Once again, keeping
windows and doors closed helps, but consider
the volume of amps and the time of day you
choose to record, particularly if it’s loud stuff likedrums. Low frequencies in particular are very
hard to contain.
Finally, you need to consider isolation within
your recording space. This can be improved to
an extent using directional mics (we’ll get to that
next), but beyond that, large screens can help
divide a space up into zones, smaller screens (or
furniture, at a pinch) can be used to ‘box’ away
amps, and small ‘reflexion’-style screens work
well on individual mics. Finally, if you have big
enough cupboards or are able to run cables
from one room to another, this is often the
best way to isolate individual
instruments or performers.Acoustics in your
recording space
July 2019 / COMPUTER MUSIC / 27the fast guide to recording / make music now <