Originally written for suite101 back on 18/10/08, now up at Xomba.

Achieving clean dialogue is a vital part of almost any audio-visual production, a few simple techniques can be employed to avoid and repair a variety of aural glitches.

One of the most common requests made by directors to sound editors and sound designers is to clean up dialogue. This relatively straightforward request can vary from a simple matter of removing a few clicks and clunks; to hours spent isolating and adjusting frequencies to remove a particularly stubborn annoying background hum.

Microphone Choice and Position

For most television and film productions, the majority of sound will be recorded by a shotgun microphone on a boom, as this is generally the simplest way to record a moving subject in this situation. However, close up shots are often taken as an opportunity to get the microphone close to the subject, which opens up a variety of issues when it comes to matching shots to sound.

Often differences in sound quality are quite dramatic between long and close up shots, especially noticeable if dialogue has been recorded from a microphone built into the camera itself. Background hums become louder, breathing, mouth noises and dialogue tics become pronounced. While most sound editing software will allow the isolation and removal, or at least patching and masking of most of such sounds, consistency of microphone position can save a lot of time and trouble.

For close up shots where the intention is to create a close and intimate or oppressive quality with the sound, if at all possible a different microphone should be used. Many microphones designed for close work in potentially noisy environments use ribbon or hypercardioid elements combined with a shield, and are particularly useful for outdoor work especially in inclement weather.

While others use an optional ‘presence boost’ to create the illusion of closeness while working from a distance to avoid the vocal dangers of closeness. At the very least a small mesh ‘pop shield’ should be employed for close dialogue recording to minimise the distortion of p, b and sibilant sounds.

ADR and Re-recording Dialogue

Sometimes dialogue recording may be distorted or damaged to the extent that ripping it all out and starting again seems the best option. While this can be effective for individual lines, it should not be seen as the easy option, as it requires considerable skill from both the actors and sound editors involved in matching performance and effect. ADR dialogue can produce a very particular effect, especially if used for a large amount of dialogue.

The sound of silence is often anything but; with all rooms and locations having their own unique sound, which can even vary according to the time of day. Recording ‘room buzz’ for later editing and patching is a common practice to prevent future stress. If there are concerns on set about problems with dialogue clarity, it is a sensible precaution to record, ‘clean’ dialogue separately on the set itself.

Habituation, Masking and Background Hum

Habituation is the process by which everyday sounds become inaudible to our ears, the hearer becoming so used to the presence of a particular sound that they no longer notice or actively ‘hear’ it. This can be a particular problem with location filming, where sounds that were inaudible on set, become loud and intrusive in editing.

Most sound editing software offers a simple if sometimes time consuming solution to the persistent buzz or hum, especially if the extraneous sound comes from a single consistent source. An EQ adjuster will allow the isolation of the relevant frequency, and thus allow it to be quietened. Care must be taken that the removal does not silence the irritant only to distort other elements.

Background noise can, however, be your friend; the steady drone of traffic can mask a multitude of aural sins. A little white noise, turned down very low can often disguise places where different dialogue takes have been cut together to match the image.

Further Reading

For a more specialised and technical discussion of many of the points covered above, Glyn Alkin’s Sound Recording and Reproduction is very useful.