Skip to content

SESSIONS-AUDIO POST-Sound for Documentaries:Preparation

Sound for documentary film is a skill where typically there are no second chances.  If you are running after an interview or have a high profile person giving you five minutes of their valuable time and you’ve improperly recorded the audio, you may have blown a key moment from your film.  The importance for great audio cannot be over stressed.  Dialog replacement will not be an option for documentary, although today, because of the popularity of reality television, it has become more and more standard to include sub-titles for indecipherable audio.  However, those audiences would prefer to hear rather than read their audio.

short shotgun

AT 4051 short shotgun mic

The demands for the audio of any given documentary project will vary wildly on the program content as well as the documentary style. A talking head program will usually have controlled interview situations and time for audio adjustments if needed.  A cinema verite or run and gun documentary may often just have the chance to get a microphone close to the action and hope for the best.  This post can’t address every situation that can be encountered however, it can advise best practices to the sound recording process.

Making documentaries requires a vast media tools skillset.   Several skills will have to be employed: from the camera and sound recordings, the transfer and storage options, to the edit, the mix and the output.  Usually by an army of one, namely, you.  A thorough understanding of the tools and techniques for sound recording is going to be essential for any documentarian.  Filmmakers often have extensive knowledge of new cameras, codecs, lenses and workflows but not understand the difference between a hyper-cardioid or an omni-directional microphone and might not know the difference between a short shotgun microphone or a long one.  But, before you can even get to the recording process, you should be applying one of the most important of your skills: listening.


To properly plan for sound the first exercise is simple – listen.  Listen to the room that you are in, listen to the location that you will be shooting and understand the consequences of the audio landscape.  Filmmakers must train their ears as much or more than they do their eyes.  As humans we spend enormous amounts of time filtering out sound.  We block out the trucks and buses, the airplanes and birds, the hums of computers and fans and air conditioning, but the microphones hear it all.  They simply record the audio environment.  The environment that you may not be “really” hearing.  Stop.  Listen. Stop again.  Listen.  Try to pull out the layers of the sounds you hear, first the fan, then the computer, then the traffic, then the wind, then the birds.  If you stop and really listen you’ll be amazed at how much is going on.  Do it right now.  Do it all day long, every day.  Learn to hear.  Learn to “listen” to your locations.  Make adjustments if you can.  No matter what, those audio recordings will be with the project right up until the finish.  Make sure every recording sounds as good as it can.


Closed ear headphones help minimize external noise

I once consulted on a doc that had numerous sound issues.  The first problematic scene was an interview of a person on a street corner.  The filmmaker chose to orient the shot so that the boom and microphone were pointing directly at a noisy street.  I asked if the composition of the shot was so vitally important to create such a noise issue.  I was told that there was no one monitoring the sound through headphones and that the shot looked good with the traffic passing behind the subject.  The sounds of this busy intersection completely overpowered the conversation being recorded.  There was a lack of understanding of just how much the audio had been compromised by pointing a directional microphone straight into a loud, evolving noise source – the street.  Of course with no one listening to the recordings it would be hard to determine the quality of the audio!

It might be easy to say, well this is something I would never do but due to the circumstances of whatever is going on as you shoot you do what you can and keep moving on.  In their case the only pair of headphones they had been using stopped working.  There are many problems that can and do happen in the heat of any given production.  The situations may not be quite as obvious as pointing a mic into a busy street but the damage is often just the same.

I’m not a purist and I understand that not all contingencies can be planned for.  But often there is no actual time logged discussing the sound beyond boom or lav and the gotchas come fast and furious in post.  For those of us who are tasked with fixing the audio track it can be a real head scratcher when you hear recordings that could have been easily fixed on set with a simple turn of the mic or an appropriately placed blanket.  Hear the location that you are shooting.  Minimize the audio obstructions.  Turn off fans, unused computers and point the microphone away from noise sources.  If a location is really loud have a second look to see if moving to another place is feasible.  Oftentimes simply an awareness of the sounds can prompt you to simple solutions.  Listen.  Many times.  It’s as simple as that.


Go to a home improvement store or look online and buy several moving blankets.  Sometimes these are called furniture pads.  They are quite inexpensive and are worth their weight in gold.  Blankets should be a part of your kit the same way a tripod is for the camera.  These blankets can be used to cover loud noise sources; they can be used to deaden reverberant spaces, they can be hung in doorways to block sound.  Just fold them up, throw them in the trunk and use them when needed.  Blankets can often be a simple noise fix and can save many hours and dollars in post.  Well worth the few dollars.


$12.00 blanket can save $$

Spend some time researching microphones and their use.  Chances are that you’ve learned a great deal about the camera, the post considerations, the media storage and the workflow.  Spend some of that time learning a bit more about audio.  Which is the best shotgun mic for your situation, short or long?  Would it be better to boom the shot or mic the person with a lavaliere?  How about planting a microphone to capture a wider area of sound?  Would a boundary microphone provide the coverage that would be required for the shot?  If these terms and concepts are new to you, if you didn’t know that shotguns come in different lengths and each one has a particular usage then next time you are on the Internet search “audio, microphones and techniques.”  You are going to be living with these location recordings through the rest of the process, take good care creating them.  Make sure that the audio captured is as sharp as your images.


Sound devices mic preamp 302

Another main tool in the recording arsenal is the microphone preamplifier.   They are sometimes referred to as mic-pres or preamps.  Most microphone preamps are a part of a mixing unit or board and are built into most digital video cameras.  The preamplifier is the device that a microphone plugs into and allows for precise control of the levels being sent to a mixer or recorder.

This graphic shows a mic-pre with three inputs.  You can see the XLR plug inputs on the left and the three corresponding knobs on the front panel to control the signal gain.  You want to record the audio levels loud enough to be well past the threshold of noise (signal to noise ratio) but not so loud as to distort the recording.

Preamplifiers are a key part of the quality of the recorded sound.  Some preamps are noisy, some are quiet, some provide strong clean gain, some not.  The quality of the recording will be determined by the quality of the microphone choice and usage, and the quality and signal to noise ratio of the preamp.  If these terms are new or strange get on that Internet machine and do a bit of research.  Just an FYI, in a general sense, the mic preamps that are included in a camera are typically not of sufficient quality to deliver excellent recordings.  If you want professional results that you will be able to sell and distribute later, (right?) use professional gear.

Bring a grab bag for your audio.  Fill it with safety pins, various types of tape, extra audio connectors and mic clips.  Bring along a mic stand or two along with some clothespins, rubber bands and paper clips.  Bring extra batteries, extra cables and most especially a bit of extra time for your audio.  If you don’t have a pin to affix a cable, tape to conceal a plant mic or a stand to put a mic in an awkward place you will lose an opportunity that may not come again.  You may never have another chance with that interviewee or that event.  Plan for the worst and hope for the best.


One final thought regarding your location audio.  Besides learning about sound and how it spreads in space, besides learning about recording devices and which tool to use for the moment you need it, besides using quality equipment and excellent recording practices like not recording too hot and keeping the microphones close – I may also suggest; hire professionals.

Professional sound mixers have been there and they have done that.  They can anticipate problems before you’ve even considered it.  They can offer solutions to problems that you weren’t even aware existed.  They have probably been on more shoots than you, worked with many different talented people and are up to date in their knowledge about their specific skill: sound.  I know that budgets are tight and particularly on documentaries, but skimping on the sound process or the quality of the recordings will have a direct impact on the final product.  Bad sound has ruined many a worthy doc.  If you can’t afford to hire a sound team for the whole shoot see if you can get someone to consult with you.  A few hours in good conversation with someone looking over your gear and your recording locations can save you a lot on the back end.  You have a story to tell, make sure that your audience can hear it.



Nagra Tape Recorder