Consistency in Sound Recording

A critical aspect in sound recording for motion pictures and video is the consistency of all of the repetitively appearing elements of the soundtrack from scene to scene. As a scene (or an event in time) progresses from beginning to end -- audiences expect the sound to flow seamlessly and continuously, just as it would if they were somehow physically present while witness to the event.

It does not matter to the audience that we have constructed this cinematic event from numerous camera angles and takes, shot over a wide expanse of actual time. On screen, it all becomes one continuous mise en scene. Actors walk & talk and progress from point A in their fictional time to point B, without delay nor interruption. That is, until the scene changes. Not merely the angle, but the scene!

Imagine that you are in an apartment and eavesdropping on your roommates. You make a pretense of moving around in order to houseclean, but really you are just trying to be inconspicuous while you watch and listen to their conversation. As you periodically change your location in the room while in the act of tidying up, you are really just editing your viewing angle of the action. But even as you change you visual vantage point, or mentally focus in (zoom) on one roommate or the other, the sound remains pretty much the same.

The audio elements within the scene normally include dialogue between two or more characters, background noise, and spot sound effects. The audio levels between the actors will vary in relation to each other; different people do not speak at the same level nor with the same intensity. But real people will not change their individual speaking levels arbitrarily, suddenly shifting from whispers to shouts to normal to whispers to normal to shouts without extenuating dramatic rationale. The ring of a telephone or the slamming of a door may shatter the monotony, but the drone of the traffic outside the window remains fairly constant.

To achieve this realistic consistency of the audio is the combined goal of the entire sound team, including the Production Mixer, Sound Editor, and the Re-Recording Mixer.

This article will deal with consistency as it pertains to the role of the Production Sound Mixer.

There are three aspects of consistency that the Mixer must be attentive to: 1) Consistency within the shot; 2) Consistency between shots within the scene; and 3) Consistency between scenes.

Within the shot, levels should remain relatively constant between actors and also between background ambiance. Actors are not expected to match each other in terms of recording level; variations are normal. But their levels should match themselves. As they banter, the actors' audio should appear somewhat constant. There should be no unwarranted sudden changes in volume, except when justified by dramatic intent.

For instance, Actor A (Tough Guy) usually speaks loud and forcefully. Actor B (Mousy Nerd) is far more timid and soft-spoken.

If we are recording with a mixing panel, we try to keep normal conversation at around minus 8 or so on the meter (which is usually a peak reading meter). The area around zero is reserved for shouts and loud sound effects. Recall that when using a peak reading meter such as that found on many professional mixers, a level of minus 8 is the rough equivalent of zero on a VU meter.

Peak meters are calibrated in terms of measuring the loudest part of the signal that can be recorded without risking distortion. It is like reading a 100% white level. VU meters are set up in terms of average volume levels, and assumes approximately ten dB difference between the average level and maximum. It is like reading a middle gray level. Zero VU (middle gray) is equivalent to minus eight or ten PEAK (white). Our industry, for the sake of convention, considers a pure tone (not really the same as voice, which fluctuates a lot) of minus eight dB PEAK to equate zero VU.

When recording in digital, as opposed to analog, consider zero as an absolute zero. In other words, NEVER let your signal peak about the zero mark! Unlike analog audio recording, where distortion gradually begins at zero, the digital domain is totally unforgiving. Less than zero; it all sounds great. Exceed zero; and you have severe problems. For best results in digital, I recommend keeping normal dialogue down around minus 15 to minus 20. That allows sufficient headroom in case an actor hits you with a loud exclamation such as a shout. But on the mixing panel, we still set the actor so that his normal dialogue is below zero, say around minus eight. Zero on the mixer might correspond to minus fifteen or minus twenty on the digital recorder.

When recording these two actors, we find that Tough Guy usually moves the meter on ou mixer to, say, around minus 6. The Nerd hits around minus 10, which is a bit lower in volume and natural. Again, we reserve levels above minus 6 or so for very loud sounds (which would translate into signals of zero to plus ten on a VU meter, but still under the absolute zero critical barrier of a digital recorder).

So as much as possible during this shot, we want to maintain this recording relationship of Tough Guy around minus 6 and Nerd around minus 10. This is especially important to do if we are opening and closing multiple mics.

In addition to the actors, we must also be attentive to background noise. If we are continually adjusting the levels of our mics on the set to balance the levels of our actors, then the side effect is for our background noise to go up and down like a roller coaster.

The way to avoid problems with the background noise is to take advantage of the acoustic properties of the mics we use in order to control the relative levels of the dialogue by means of microphone positioning (distance) and angle rather than by electronically adjusting the gain (volume) at the recorder or mixing panel.

Shotgun microphones are more sensitive in the front ("on axis") and less sensitive from the side ("off axis"). Therefore, in order to balance the levels between Tough Guy and Nerd, the boom operator should hold the mic closer overhead to the Nerd with the front of the mic aimed more towards the Nerd, and allow the Tough Guy to strike the mic from more of a side angle and from a little further away. The increased distance to the mic along with the reduced sensitivity of the off axis angle will effectively reduce the volume of the Tough Guy in relation to the Nerd without affecting the constant level of the background ambiance.

As you can well imagine, the boom operator is a very important player. That is why boom operators need to be chosen carefully by the Mixer and cannot merely be selected from the pool of bystanders who aren't busy in the shot. This is also why it is very important for boom people to be provided with a good headphone feed of the program material.

When it is time to record another take of the same shot, once again it is critical that the Mixer pay attention to the relative levels of the characters and background. Footage from this take may be combined later on with past or future takes, so consistency of sound quality and levels is important.

When the camera changes its angle, the Mixer must be especially attentive that the levels of the new shot match and be intercuttable with the previous angles. Tough Guy should still be recorded around minus 6, where we established him before. Likewise, Nerd should remain around minus 10, where he was previously established. Remember, the audience should not be cognizant of an edit or camera angle change within the complete mise en scene; the action must appear to flow seamlessly from point A in time to point B in time.

Minor changes in angle do not motivate drastic changes in audio. Panning or cutting from one close-up to another of two people standing around talking does not constitute a significant perspective change. Levels and background are expected to remain constant.