Achieving clear, crisp dialog and sound effects on a film or video production is no easy task. Production sound mixing is a craft that requires a blend of technical expertise and proper tools. The key to good sound gathering is to work from some basic strategies, and then work up from there.
Anticipate instead of react. Don’t limit yourself capability-wise to what you have been led to expect based on the production meeting. Things often change at the last minute, and producers/directors are notorious for not bothering to inform all of the crew. Be prepared for as many contingencies as possible. For instance, if the shooting schedule calls for only interior interviews that day, I would still bring along a good exterior shotgun mic and windscreen, just in case someone decides that a long “walk & talk” against a scenic city background is visually more interesting than a talking head in a cramped office.
Think in terms of what is known as the Hierarchy of Microphone Techniques. This hierarchy serves as your starting game plan in approaching a scene in terms of microphone selection and utilization.
- Overhead boom
- Selection of overhead mics – which pattern of condenser is best?
- Boom micing from underneath
- Boom mics as plant mics
- Lavalier mics as plant mics
- Lavalier mics as body mics
- Lavalier mics as wireless or radio mics
- Overhead miking from a fishpole or studio boom is the most favored technique in the feature/TV/commercial industry. It is probably the best choice 90% of the time. Generally, overhead miking will yield the most natural sounding dialog with the least amount of mixing and editing effort. It provides a pleasant blend when there are multiple actors involved. Two, three, even a small group of people interacting can all be recorded from a single mic.
- A mic on a fishpole or boom allows for a fair amount of physical activity and movement by the talent. Actors are free to enter and exit a scene, move around, jump around, climb around, etc. There are no trailing mic cables to inhibit their range of motion.
- An overhead mic will pick up sufficient sound effects, footsteps, and hand- prop noise to give the soundtrack a full texture. Because the faces are closer to the mic, dialog will dominate the track, but other sound effects will still be audible.
- Audio perspective is easier to maintain with an overhead mic. On a wide master shot, the mic tends to be higher so that the resulting dialog seems thinner and more “distant.” On close-ups, the mic can be lowered, giving the sound much greater presence and “near-ness” to the screen.
- Narrower patterns, such as shotguns, have greater reach but exhibit more reverberation in a closed interior. For that reason, shotguns are preferred for exterior use or sometimes for use in a very dead soundstage. Besides a build-up of echo in an interior, a shotgun used overhead tends to be physically unwieldy in terms of headroom. Their narrow pattern also makes cueing from actor to actor very critical.
- Shotguns, like telephoto lenses, will compress the background in terms of the foreground. In a photo, a distant sunset will appear very large and very close to a foreground sailboat. Similarly, shotguns will magnify background sounds and ambiance in relation to the subject. That is why the best way to utilize a highly directional microphone is with nothing behind the subject (i.e. the mic looks down at the subject, “seeing” only quiet dirt past it; or aimed upwards at the subject, seeing only silent sky).
- Aiming a shotgun horizontally should be avoided, except for miking certain sound effects. Wider pattern condensers (cardioids) and ribbon mics provide the mellowest sounds in terms of reverberation or room echo, but also have the shortest effective range. They must be kept relatively close to the actors in order to isolate the dialog. However, since the cardioids are often used in cramped interiors with low ceilings, excessive headroom is not usually a problem!
- In between the wide cardioids and the narrow shotguns are the wide hypercardioids and the narrower hypercardioids. Their selection would be a trade-off between mellowness versus effective reach.
- In addition to echo and reach, another factor that comes into play when selecting a boom mic is that of spread. Scenes involving tricky blocking and/or multiple actors might be better served by a mic that does not require as critical a targeting, even though it would be a compromise against reach and punching the dialog.
- One very useful trick in balancing a strong voice against a weak voice is to take advantage of the microphone’s natural pattern. Favor the weak voice on axis, and let the strong voice strike slightly off axis.
Handheld microphones (performer or reporter mics) aren’t used very frequently in theatrical production, but can have their uses. Dynamic mics are ideally suited for recording loud explosions, since their elements are virtually indestructible. A dynamic mic used relatively close-up (6 to 9 inches away) works excellently for isolating speech from a noisy background, such as for on-site voiceovers or talking head (mic seen on camera).
Staged scenes involving the use of a handheld mic (as a prop) should be recorded exactly that way, “as a prop”! Use a boom mic to actually record the voice, unless you want to be at the mercy of handling noise and inconsistent mic placement.
For man-on-the-street reporter interviews, provide talent with an omni- directional condenser (or electret) microphone. That will give you some consistency, regardless of how well the reporter pays attention to cueing the microphone between himself and the interviewee.
But what if there are physical obstructions in the set that prevent deploying a microphone from overhead?
The boom mic can be fishpoled up at the talent from knee, thigh, or waist level with good results. The sound will be slightly more bassy than miking from overhead, but still quite usable and acceptable. Note that a mic aimed up at a person tends to pick up more of the chest cavity, thus accounting for the increase in bass.
Personally, I find that it is much more difficult to boom from below, due to the presence of set furniture or the choreography of foreground persons. Camera operators also have to be much more careful, since it is more likely to widen the frame to show more of an actor’s torso than to show more empty headroom above. Nevertheless, there will be many shots where miking from below is the simplest solution.
If the overhead microphone does not have to move, does it make any acoustical difference whether the mic is held up by human hands with a fishpole or rigged to a C-stand or clamp?
The definition of a “plant” mic is any mic fixed in place on a set. It can be a boom mic secured by any imaginative or convenient means over a dialog mark. Or it can be a boom mic secured in an “underneath” position, such as behind a table or potted tree. Or it can be a miniature lavalier strategically attached or hidden anywhere in the set.
Which type of plant mic you choose depends on the situation you are faced with.