LOCATION AUDIO FOR ANY
by Carlos E. Martinez
Copyright © 2003 Precision Audio Products Inc.
Even if this may look like a technical
and specific article, it is important for directors and producers to read these lines too,
because sound is far from being a secondary area. There are many questions, related
to audio, that must be solved or talked about before shooting begins. Sound matters will
also be a big concern in post-production. So a thorough knowledge of what is involved is
mandatory to people involved in related areas. As I said above, particularly for directing
Picking quality audio on location is now a reality which is becoming more and
more delicate with the widespread diffusion of digital mini-DV camera. But the growth of
the so-called digital films has taken to the
market productions that show many weak points on their audio tracks, particularly
problematic when the film is fiction and not a documentary. Let's see which these problems
are and how we may handle them. The trick is getting that for a low budget.
The camera microphone should rarely be used because of its placing
|Until now, the
final destination of most semi-professional jobs shot with those cameras was television,
generally cable channels. Many also were documentaries, where the only location sound was
a speaker usually facing the camera.
For that type of location sound the way out is generally very easy: use either a hand microphone, "news" style; a lapel mic connected directly to the camera; or a wireless mic. It is important to emphasize that in such cases many of these professional speakers generally know how to speak or have learnt how to doing that job.
Things get more difficult if what you are after is a more authentic style, catching the direct sound of the location you are recording at. Which is particularly problematic if you have no interviewer and the person who should speak to the camera does not have any professional experience on how to do it, that is to say any average person. Things get even worst if you intend to use the camera microphone. Although that is very rare now, fortunately.
In spite of all these problems you generally get away with it for several
1) Because most times a speak-over track is added during editing.
2) Because the small speakers of 90% television sets hide most defects.
The latter has always been problematic, since hiding instead of showing is
sometimes dangerous. Someone may raise the carpet and see what's underneath. This is
already happening, because of:
A) FICTION VIDEOS, where you can hide little, are getting more
popular. You can always dub dialogues, but dubbing is a foul word in television. Except on
some foreign videos or films.
B) LARGER TV SETS, which have become more popular and affordable,
usually have a better sound. Besides that many people are already connecting them to their
main audio systems (home-theater, etc.)
C) KINESCOPING is taking many features shot in video to movie
theaters, which is particularly worrying when shot in mini-DV.
How to deal with all these problems then?
My proposal is implementing a feature film methodology. And what methodology is that?
Lets talk about some film audio
techniques for location sound. Not willing to be extremely perfectionist, there are a
minimum of demands that should be followed:
1) Using a dedicated soundman or boom man to handle the mics.
2) Using good quality directional microphones.
3) Using wireless microphones, or at least hard-wired lapel types
4) Using external preamplifiers or mixers
5) Using good quality headphones all the time for monitoring your recording.
Let's see why everyone of these items is so important.
Hyper-directional microphones can be short or long
The first demand that should be followed for a quality location audio, is to
have a dedicated audio person during all shooting, if possible also during pre and post
production. The soundman will provide a
focused attention to the dialogues or interviews.
Sometimes the sound is the last thing production people will think about.
Always arguing budget limits reasons, a soundman is rarely used during pre-production. Why
not doing things right since the beginning?
Which microphone to use?
Doing things right does mean calling a soundman to talk about the project audio matters. It's very important that the soundman checks the locations you are going to shoot at to find out about potential acoustic problems.
As we are talking low budgets here, there might be two choices to lure a soundman in at this stage: to ask him to do the pre-production for free or to use good arguments for him to feel guilty... so he will do it for free. If experienced soundmen are reading these lines, or someone willing to become a soundman, keep in mind that the results are going to be better if you do some audio pre-production. Less unexpected surprises may mean fewer compromises.
Using an experienced soundman involved will also be important if you can't check what the acoustical conditions will be, like a live concert or event. Previous experience may allow foreseeing what the problems might be and what to use.
What can you do when you don't have a soundman at this stage? Not much, except if you can identify and isolate the acoustical problems yourself. You might get some ideas from our articles, but you will need to train your ear for doing so.
Whether in the pre-production, or during actual recording, we will have to
face the first problem of location audio: acoustic reverberation.
Reverberation occurs because of successive ricocheting of sound waves on different surfaces. Some surfaces absorb, others reflect. Actually the problem is that absorptions or reflections are not linear, which means its not the same for all frequencies. If they were it would only be a question of rising or lowering your recording levels. Unequal (nonlinear) reflection and absorption will result in peaks and dips of great magnitude. They will interfere with your sound source, affecting the intelligibility of what is said or played.
Keep in mind that our ear and brain correct most of these problems in normal listening: thats why we very rarely perceive them as problems. But when you put a microphone and use a headphone to check a highly reflective environment, you will see how the ambience usually supersedes over the sound sources. And its those sound sources, persons or musical instruments that we need to pick. As cleanly as possible.
Acoustic foam or some blankets can help with reverberation problems
Microphone pattern or directionality can help decide which type will serve us better
The next problem on a location
(or everything that is not a studio) is ambient noise. Even if your places are
acoustically satisfying, there might be some several external noises: traffic, airplanes,
trains, industrial noises, AC, etc.
The first tool to helps us in most circumstances with these two problems is
the directional microphone. There are several
degrees of directionality among microphones types, going from very little directionality (omnidirectional, more open) to the
ultradirectionals (hyperdirectional, more
sensitive in one direction or two).
In fact the options are plenty, including some models which are quite
affordable and still showing remarkable quality.
Most modern directional microphones used in film/TV jobs are capacitive
types, or condenser. They need a DC supply (internal or external) in order to work. They
use a diaphragm which is polarized with a very low electric current. Moving air waves
excite this diaphragm and make it vibrate, causing very small electric variations. These
variations are amplified and reproduced at the output as audio.
The other type is the so called dynamic microphones. They do not need a
supply. Their diaphragm vibrates when hit by the airwaves, these resulting in very small
electrical signals, later on amplified as audio.
The large availability of condenser microphones, and their price fall, practically eliminated dynamic microphones as tools for location sound. They are still used for hand microphones, as they are quite sturdy. Though they do not need a supply, they do require a good preamplifier, because their output is quite low.
To tame some acoustic reverberations (echoes)
its preferable that the microphone we are using has some filter switch that can cut
lower frequencies. Its in 150 cycles (Hz) and lower frequencies where most problems
are. On some microphones you can even select what frequency to cut, usually 80 or 150 Hz.
But be careful: the idea is cutting or equalizing as less as possible. How do
you set that? By paying attention to the voice or instrument you are going to record.
Filtering should not change the tone of a particular sound. The key word here is intelligibility. If cutting at 80Hz improves that
intelligibility, there is no reason to cut at 150Hz. The arbiter for that is usually the
soundmans ear and experience. In any case you should get familiar of how things
sound when improved or when you over equalize.
Dont forget that in post-production we are going to improve your audio,
using tools that are more precise. If we cut too much during shooting and the sound gets
too bright, its going to be difficult getting back what you lost by over filtering.
The other important way to control
reverberation is distance. That is to say that the closer we get to our sound source, this
source will prevail upon other interferences. To do that you use fishpoles or booms, that can be from 4ft to 20ft
long or more. You put the microphone on one end of that pole and get as close as you can
to your sound source, pointing from up or below.
To avoid mechanical noises in your audio track, due to boompole handling, we should use an elastic mic suspension, where bands or tapes of rubber will partially isolate the microphone from vibrations. It is said that the microphone is floating in the suspension. You should check that it properly does so when you select your suspension type.
Microphone, elastic suspension and foam windscreen can be light and go a long way.
A "Zeppelin" style windscreen can keep out noisy winds and protect the microphone at the same time.
|Wind is another
problem that can interfere with our intelligibility, since it will cause vibrations in the
mic diaphragm. To avoid it we use windscreens.
They can be foam, silk, wire, etc. Usually a combination of these. The advice here is the
same as with filters: the less windscreen the better. If we can get away with no screen,
we use none; if we have to dress up everything because we go to the Himalayas, then we put
it all. Most of the times you will need at least a foam windscreen or some sort of
Zeppelin shaped one. Its called that way because it resembles that
It is now important to emphasize another concept. In image we have the wide open plane, medium plane and close-up plane. They always relate to the size of the actors in the screen frame. For audio it's very much the same. The closer the distance between microphone and actors you get a different audio quality. Even if there's little or no reverberation on the set, the voice will sound different depending on the distance between microphone and sound source. We call that the sound plane.
It is very important to emphasize this concept, because one of the problems you can have when dubbing is some artificiality in the audio quality. Everything tends to sound close and the same when dubbing is not done properly. For that not to happen adjust the distance between microphone and actor according to how it is on the screen. Make the actors walk towards the microphone or away from it. The growing use of real location sound, both in TV as in movies have, in my opinion, made everyone more aware of such fakeness in dubbed films.
Location audio went through two great leaps in the '80s and '90s: new lapel
microphone types and reliable wireless microphones. Now we can have affordable tools for
location audio, fitting almost any budget.
Old lapel/lavalier microphones picked all audio in close-up, independent of
the distance between sound source and microphone. Everything tended to sound close by.
That audio conflicted with the sound plane picked by the main microphone, usually on a
The boom-mic sound varied accordingly with the distance between mic and
actor, which also depended on how wide the framing was. A close up allowed you to go
closer with the boom, a wider framing made your boom-mic go farther up. But the lapel mic,
sometimes on a wireless transmitter, sounded always in close up.
All this changed when new lapel mic types were released
in the mid '80s. Their sound belonged on a medium plane. Using these microphones allowed a
better integration between lapel and directional mics. No major conflicts anymore, as the
medium plane is the most usual when you block a scene having actors.
This improvement was so important that more movies started being done using mainly wireless microphones. Sometimes using just the directional mic became the exception.
Don't you dare think that wireless mics are trouble free.
A wireless microphone will usually help keep dialogues clean
The first one is where to place the transmitter generally under some
clothing. Securing the lapel mic causes mechanical problems (clothing noise, rubbing,
etc.). The fabric also acts like a filter, sometimes cutting frequencies that leave the
voice of the actor sounding muffled or uninteresting.
Radio interferences are also a problem, that can be ameliorated a great deal
but which may rear their heads on many circumstances.
Another thing is how many wireless microphones we will need to use for all
actors on a scene.
The best of both worlds, to have a balanced and intelligible sound, is to use both directional and wireless microphones at the same time. We use one or two wireless in the main actors, and then follow the action with the fishpoled directional. We balance it all using the mixer or preamplifier. Sometimes we can record every microphone in separate audio channels, to be mixed later on.
PUTTING IT ALL TOGETHER
A microphone preamplifier will improve your levels
The fourth element, that agglutinates
it all, is the preamplifier or mixer. The quantity of channels will depend on how many
microphones are being used. It can go from 2 and up to 8 or more. Though rarely is more
than four. Not surprisingly, most mixers in the market have four channels.
In the mixer we adjust the level of each microphone and filter low frequencies a bit. Peak LEDs or VU-meters are used to set each microphone's level and the output too. Sometimes there are limiters that help prevent unexpected audio peaks, attenuating them to a preset level. Level adjustments should always be set so that limiters never work, as far as possible, though always having a good modulation levels.
|Our fifth tool
are the headphones, that we use to set the
levels and everything else. It is very important that the soundman is familiar with the
headphone he is using. If hes not he may well end up equalizing more or less than he
should. The headphone will also determine the best point when fishpoling, particularly
when following an actor that is constantly moving.
Up to here we have roughly explained how location audio is done in movies. Location audio on film series or soap operas is very much like it too. The task is getting a clean dialogue, to which you will later add music, sound effects, etc.
Quality closed headphones are essential
When budgets are low, some tools can't be afforded. Like not being able to
have several wireless microphones, or a 4-channel mixer. But there is a minimum package
that I think you must have: a directional microphone, a wireless microphone, a 2-channel
preamplifier or mixer and a good headphone.
A top package
Why using two microphone types, if your budget is low?, you may
ask. For the same reason that in the camera we are going to use different zoom settings.
The moment we have more than one actor things get complicated, particularly if we are
shooting in real locations. And these are the types we will mostly have in low budget
productions. In fact, those two basic microphones will help us deal with most difficult
situations we may face.
There are also a quality reasons: the sound of a directional microphone is
generally less restricted than a lapel's. The directional's sound will usually
be better, but we are not going to be able to use it all the time, or use the lapel all
the time. The best thing: always use both.
There's another problem: mini-DV camera limitations.
Setting audio levels in those cameras is precarious, nonexistent or quite unpractical.
Some digital cameras use internal menus. On some others there are little pots or switches
that we may have to set, up or down, for each sequence.
That's why its better using a 2-channel preamplifier or a mixer to set
the microphones levels. On the camera we adjust the audio internal level just once: when
shooting starts. It's advisable not to change those levels until all shooting is over. You
will have to do periodical checkings though, to verify that nothing changed in the camera
during shooting, particularly when batteries are changed. Menu settings have separate
batteries though. Double check if external knobs were moved, using existing markings or
some you make yourself.
During each sequence set the level for each microphone on the preamp
according with rehearsal.
Important!!! You must keep the same level setting and
equalization on each sequence. If we change one or the other, when editing audio you will
have differences in the sound and/or ambience on that sequence that will be hard to
adjust. Change recording settings only when you move to another sequence.
To improve the audio you are picking on a directional microphone, you need to
go as close as possible to the sound source (actor, instrument). Dont go too close
though, or there will also be differences in sound planes that will be difficult to
integrate later. The wireless mic is also adjusted once. When you change scenes or go to
another settings you can re-adjust levels if necessary.
Don't forget!!! Record two or
three minutes of ambience sound at every set you shoot at, keeping the same
shooting/equalizing levels for that sequence. Ask for silence at the end of each sequence
shooting and record that ambience. This "silence" will be essential during
editing to fill in audio blanks which have no dialogue.
The headphones output level also has to be the same on
each sequence. It's better to find a way to monitor audio always from the camera, if you
are recording audio on it. It is also a safe way for verifying nothing was changed on it.
As most mini-DV cameras have unbalanced inputs, which are more sensitive to interferences,
the distance between the camera and the microphone, preamp or mixer should be short. So
3ft or 6ft headphone cable should be enough for your monitor.
Many of the above techniques also apply when shooting with full professional cameras, whether DV-CAM or Betacam, analog or digital.
Up to here we just had a short general introduction to
minimum techniques you should follow to get a quality audio track when shooting on
location. In the future we will go deeper upon these and other practical aspects related
to picking location sound, backup in DAT or MD, time-code, etc.
Copyright © 20o3 Precision Audio Products Inc.
PRECISION AUDIO PRODUCTS INC.
Phone: 305 776-0732
Fax: 954 747-1787