Audio Recording for the Uninitiated
The popularity of camcorders has
introduced a lot of people to the mysteries of live audio recording. Most owners of
audio/video equipment had been content with professionally recorded material. Then along
came the camcorder, which, among other things, recorded sound. All of a sudden, millions
of camcorder owners had to deal with microphones and their quirks. Camcorder manuals
rarely go into much -- or any -- detail about recording technique.
The microphones built into camcorders are, of course, very
convenient, but for many recording situations, and for virtually all serious music
recordings, you should consider bypassing the interior microphone and using external
equipment. Making good recordings is a skill that takes a lot of rehearsal and experience,
so don't be disappointed if your first attempts fall short of the sound quality you are
used to from movies or CDs.
The first thing to consider is where the recording is to be
made, as that will affect your techniques profoundly. Every location has its own acoustic
character, and it may be appropriate to include some or all of the ambient sound in your
recording. As a rule, the closer you place a microphone to your principal subject, the
more ambient noise you will eliminate. That's because, in an enclosed acoustic space, the
overall reverberant sound is fairly constant throughout, and will hit the microphone with
about the same force wherever you put it. But the farther you place it from your main
source, the more you will have to turn its level up, and that will increase the ambient
sound's level as well.
Outdoors, placing the microphone some distance from the
main sound source won't pick up the sort of echo characteristic of enclosed space, but it
will tend to pick up things like airplanes flying over. If things are quiet, however, you
can often achieve an interesting atmospheric effect by intentionally placing the
microphone at some distance and cranking the volume to exaggerate a brook babbling nearby
or the rustle of leaves.
Using microphones outdoors has one distinctive problem:
wind. Even a light breeze can create enough disruption to obliterate what you're trying to
record. The wind filter included in some camcorders may get rid of a bit of this by
rolling off the low frequencies, and using a foam pop filter may do some good. But the
only real way to avoid the effects of wind is to make sure they don't reach the mike.
Blocking the wind with a piece of board or a cushion often works, or you can sometimes
just stand upwind of the microphone. If there's no way to block the wind, it's usually
necessary to scrap the recording or find another place to do it.
If it's not feasible to move the microphone close to your
subject, the more directional a model you use, the more it will discriminate in favor of
sounds from one direction and against those from another. It's often possible to arrange
things so that the most sensitive portion of the mike's pattern is aimed at the subject,
and the deadest at the unwanted sound.
If you're faced with music being played in a large space,
it's usually best to place the microphones at some distance from the musicians so that the
natural ambiance of the room comes through. If the perspective is too close to the
instruments, the sound will be much "drier," and while that may be appropriate
sometimes, it usually isn't in a large reverberant space.
On the other hand, if you are trying to record human speech
in the same hall, you should try to place the microphone as close to the subject as
possible. Sitting halfway back in the hall and aiming the mike toward the subject is
almost always unsatisfactory; if necessary, you might try sitting next to a public-address
loudspeaker and picking up the sound from there. This is always a last-resort approach.
In smaller rooms, you should aim for as little of the
natural ambiance as possible, as it tends to lend a "boxy" sound to a recording.
A combination of sound-deadening materials, close placement of the microphones, and use of
directional models usually results in the best sound.
When recording voice, it's often sensible to place the
microphone slightly off to one side so the speaker is not talking directly at it. This
should substantially reduce any verbal explosions. If it doesn't, you can add a pop
filter, designed to reduce the effect of certain sounds -- Ps and Bs, for instance --
uttered close to the microphone.
While the best intelligibility is usually gained by placing
the microphone as close to a speaker or singer as possible, it may have adverse effects on
the overall spectral balance of the sound. Directional microphones exhibit a phenomenon
called "proximity effect": As the sound source gets close to the microphone --
less than two feet, say -- the sensitivity to lower frequencies begins to rise.
Omnidirectional microphones don't exhibit this effect.
While it is sometimes desirable to hold a microphone in
your hand, that often leads to physical noises being picked up, which can be very
distracting. One way to avoid this is by using a lapel mike that clips to clothing or,
alternatively, supporting the microphone with a stand or boom. Some models are provided
with their own table stands, and these are often all that's needed, but if you intend to
use detachable stands or other arrangements such as an existing gooseneck mounting on a
lectern, you should make sure that the microphone you choose can use these. Fortunately,
most supports use a standard-sized mount, and the majority of microphones will accept it.
Often, however, extra devices are necessary, or at least
can make your job easier. If your recorder lacks microphone circuits, the minimum you will
require is a microphone preamp to boost the low signal to a level the recorder can work
with. Usually the most practical method of providing such a preamp is by using a
microphone mixer, which has one or more built in.
Every recording and every piece of recording equipment is
different, so learning to make good tapes takes a lot of trial and error. But when you get
the knack, it's hard to beat the satisfaction of listening to recordings you have made
yourself.
...Ian G. Masters
ian@mastersonaudio.com
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