In an ideal world, your edited project
would be sent to an audio post production house for sweetening by
an engineer, but in the independent world, and increasingly in the
budget-strapped world of television post production, you as the
editor may have to perform the final sound mix.
The most basic thing is to be aware that a sound mix is not a recreation
of reality. It's something artificial that serves your creative
purpose. This is both empowered by and limited by capabilities of
the technology you and your audience will use to communicate, and
by the real world environment in which they will experience it.
Of course, there will be some situations in which you will have
problems that need to be fixed with equalization, noise reduction
or other techniques, but for now, let's stick with the basics of
setting appropriate levels. Firstly, let's look at a few technical
elements, then some practical ideas.
Dynamic range: technically, this is the difference between the
loudest and the softest sound your equipment can produce. In a real
application, it's the difference between the loudest and the softest
sound your audience will understand. This will vary with circumstances.
In a cinema, you have high fidelity equipment in a controlled environment
that gives you more flexibility. For television or internet delivery
you are more limited and frequently need to think of the worst case
-- say an old TV or small speakers in a laptop. Your audience may
also be in a noisy environment, like a living room with other people
talking or involved in other activities.
For these reasons, a practical sound mix tends to stay within a
smaller range of volumes, a smaller dynamic range, than the sounds
we hear naturally. Also keep in mind, in the physical world we naturally
adjust our relationships to sound sources to achieve a comfortable
"mix." If something is loud, we turn away from it. If
something is soft, we lean towards it. We move to block noise or
to increase the clarity of something we want to hear. Your audience
will probably not want to constantly change their positions or even
the volume of their equipment while watching your work. So, you'll
want to keep your sound within a comfortable listening range most
of the time.
There are also technical requirements that limit the practical
range of volumes you can use. This is particularly true for broadcast
media, where signals are highly controlled and often severely compressed,
but it also applies to other delivery systems where there are standard
expected uses of sound levels. You want your DVD or media file to
play at more or less the volume the audience is expecting.
To help you with your sound mix, there are usually level meters
on your edit system. They are marked in decibels, written as dB.
A +10dB change means something sounds twice as loud to us. A -10dB
change means it sounds half as loud. Think about this when setting
your audio levels. When you're watching television, you wouldn't
want something to suddenly get twice as loud, or twice as soft,
would you? For that matter, when you are talking with somebody you
wouldn't want them to suddenly get twice as loud. You might do this
for dramatic effect, but most of the time you are going to want
to stay within a smaller, more comfortable range of sound levels.
The final thing to keep in mind is that your edit suite is not
a very good representation of the listening environment your audience
will be in. You are probably sitting close to your speakers; perhaps
they are studio quality monitors. It may also be a controlled, quiet
environment so it's easier for you to hear nuances and subtleties
that the audience may or may not. Conversely, your audience might
have a home theatre system with a subwoofer and much better speakers
than you do. Something that seems unimportant when you are editing
might be jarring on their system. For this reason it helps to take
especial technical and creative care.
Now, some practical considerations.
At the beginning of a mix, it's common to mute all tracks except
your primary voice. This might be a mixture of dialog recorded on
location, dialog or voice over recorded in a studio, sound on tape
or perhaps in some cases even singing or other vocal performance.
Even though you may be adding atmospheric sound and music to your
mix, keep in mind that your main purpose is for your primary voice
to be intelligible to your audience. If they can't understand what's
being said, you'll lose them very quickly.
Decide what level you are mixing for in general. A common level
is -14dB, although sometimes other levels are used. Your edit system
may have a default recommended level: typically around where your
level meters turn from green to yellow. Pick a level. Stick to it.
Watch your meters. Use changes in volume judiciously. Remember this
is art, not reality. If there are places where your sound gets much
louder or much softer than your target level, be aware of why you
are making this choice creatively. For example, a loud surprise,
or encouraging the audience to strain to listen to create tension.
Note that these are both exceptional situations, after which you
would return to your target level for general listening. Your edit
system should allow you to bring levels down as much as need be
and give you a small amount of standard boost. Both Avid and Final
Cut Pro also have separate tools for boosting a signal more than
+12dB, should you need to do so.
It's often helpful to set rough levels in your source material.
Well recorded sound should be at a consistent level, so once you
set a level in your source it may be good for any time you use that
clip. Also, prerecorded music may import into your edit system at
an unusually loud level and need to be adjusted for any kind of
You should be able to set the volume on your monitor speakers to
a comfortable level and then leave it for the entire time you are
mixing. If you find yourself changing the volume on your monitors,
it may be that the levels in your mix aren't consistent. Keep an
eye on your level meters to make sure you're hitting your target.
You may also find that your ears become tired after you have been
mixing for a while and that you'll be unconsciously making tracks
louder to compensate. Your hearing will also tend to become duller
as your ears tire. This will happen more quickly if you have your
monitors very loud and may happen more quickly if you are using
headphones. It's helpful to take a break every so often and get
away from amplified sound to give your hearing a chance to recover.
Watch out for some common things that people do while talking.
Sentences often start loud, level off for the most part, then trail
away towards the end. People will also tend to get louder again
if they take a breath during a sentence. It can be helpful to smooth
this out a little. Often the changes you need to make will only
be small ones between 3dB and 6dB. Be careful any time you notice
yourself making a large change and make sure it is genuinely necessary
because of changes in the source.
Next, unmute your foley, ambient or natural sound tracks. These
sounds add a number of important factors to your mix. Natural sound,
foley or sound effects add impact, or at least make sense of actions
we see on the screen. They typically don't have to be very loud,
although they may be for specific effect, particularly surprise.
Most importantly should not distract from any dialog or other primary
Ambient or natural sound tracks also help establish time and place
and give flavor and depth to scenes. Like foley and sound effects
they should be used selectively to specific effect. Ask yourself
what each sound is adding that helps tell your story. If there is
something you don't like in your track, don't just make it softer.
Unwanted sound is "noise". Remove unwanted sound altogether
or replace it with something you do like.
It's important to maintain continuity in ambient sound and make
smooth changes in it. Abrupt changes will be particularly noticeable
on high-end sound systems. Your sound operator may have recorded
"room tone" (sometimes called "world tone" if
you are shooting outside) which is typically around 30 seconds of
ambiance that you can lay in areas of silence or under edits to
help maintain continuity of sound. Think about the type of edits
you are making and what may sound abrupt or discontinuous.
Once you have a fairly consistent mix of primary voice and your
other sounds put together, it shouldn't be difficult to add music.
Most prerecorded music will already have been mixed to a fairly
consistent level. Classical music may change more dramatically and
more abruptly, as might an original score. Frequently you can determine
two basic levels at which to cut in your music - one level where
the music is the point of focus and a "ducked" level where
the music will be under your primary voice. The difference between
these levels will often be between -6dB and -12dB. If you find yourself
ducking more than that the levels of your primary voice may not
be consistent. You may also need to bring the music down further
if it changes, such as extra instruments being added.
It is sometimes difficult to balance music consistently with voice.
Make sure your music is panned correctly if it is in stereo as this
will help separate the two. Voice is usually mono and panned center.
The balance will often sound different on different televisions
or sound systems. If in doubt, favor your primary voice track.
If you find different parts of your mix competing remember your
main purpose - to make sure your audience can understand your primary
voice. In particular, watch out for sounds that compete directly
with your primary voice, like other voices in the background, singing
or instruments such as electric guitar which have similar frequencies
to the voice. A common error is to allow your primary voice to become
masked by other sound elements, but not to notice it because, as
you've been editing, you have already heard it dozens of times and
know what it says. Your audience, who hasn't heard it before, may
have a harder time making it out.
When balancing different elements of your mix, keep in mind that
it's relative whether one part is too loud or another is too soft
and you may mistake one for the other. If in doubt, go back to muting
all the tracks except your primary voice and make sure that it is
consistent. Then, bring in ambient and other sound and make sure
it is not unnecessarily loud. Finally, listen again with your music
added back in. This will help make sure you are identifying the
Once you have your mix, there are several ways you can test it.
One is by listening to it loudly, another softly. Let's call the
first the "threshold of pain" test. Just kidding. Listening
to very loud sound for extended periods of time will dull your hearing
temporarily and may damage it permanently. Anyway, listen to a general
part of your project and turn your monitors up to a level that is
at the top of your range of comfortable listening. Now play the
whole thing. Anything that is much louder than the first section
you were listening to should be uncomfortably obvious and you can
The opposite technique is to listen to a general part of your project
and turn your monitor level way down, so that you can just make
out what is being said. Now play your entire piece. Anything that
is significantly softer than the first section you listened to,
you won't be able to make out, and can be adjusted.
The final test is a simple reality check. Make a viewing copy of
your project and try it on different pieces of equipment and in
different environments. Try it on a cheap TV. Try it on a home theatre
system. Try it on a laptop. Have other people listen to it. If you're
having a screening, listen to it on the system that will be used
for the event. The response of both consumer and event sound systems
will most probably be different to those of your studio monitors.
The only reliable test is real world environment.
Note: Craig Tollis is an Atlanta-based editor
and Filmmaker with ten years of experience. He will gladly answer
your editing questions. Just email: firstname.lastname@example.org.