Sample Clip in Car

Earle used a clip, shot in a car, to demonstrate doctoring the sound track in an editing suite. Shooting in a car with the microphone seeing the nearby hard reflective glass surfaces gives us highly coloured sound. Then we have to contend with vehicle noise, passing traffic noise, such as trucks, as well as the speaker raising her voice when noise becomes apparent. While it is desirable to use fixed audio gain settings to avoid the volume pumping of automatic audio gain in this situation, we revert to the automatic setting because of our lack of control of the actual sound levels. The volume pumping action makes post-production more difficult.

Editing Suite

Even though he is a seasoned professional, it is worth noting that Earle avoids the high cost of Final Cut Pro and MacIntosh computers and uses Sony’s Vegas. It does the job, to the highest professional standards, in acceptable delivered format, for $600, without needing a herd of extra addons. So, you have no excuse to waste your money for meaningless status. Then there’s your really cheap writer who’s very happy with his $45 Magix Movie Edit Pro for HD.

Using Audio Filters

Using a high cut filter to remove high frequencies, removes significant amounts of high frequency noise. One must be careful when cutting below about 5 KHz as then one will be removing the sibilance frequencies critical to speech intelligibility. The high cut filter will remove the high frequencies that make up high fidelity, but this is the tradeoff for reducing objectionable noise.

Using a low cut filter will remove the low frequency rumble noises. This time we risk cutting the low frequencies that give the voice warmth, trading off audio quality for reduction of objectionable noise.

Notch filters can be used if a noise is of a very specific frequency. In our sample, the main frequency of a passing truck was effectively removed. Because the notch was very narrow, the effect on the voice was unnoticeable.

Monitoring

It is important to use a good quality speaker system when doctoring your sound track. This is especially important for very low frequencies which are inaudible in a cheap speaker system, but may be overwhelming when played on a good audio system with a powerful subwoofer. Similarly, high frequency noise may be very objectionable on a good sound system, and be absent on a cheap speaker.

While doing the doctoring, the particular flaw we are trying to reduce is played in a loop while settings are adjusted. After we are satisfied with our settings, a comparison to the original should give us great satisfaction. Another good practice is to play the clip on a cheap speaker system, to ensure that it still sounds good on this more typical sound system.

Using the Audio Timeline

There are many ways to use the timeline features of your editing program to control the audio segments. Earle reverts to the time proven technique used before computers. One assigns each short part of the clip a separate channel, as in the days of mixing boards, where the parameters are adjusted until satisfactory. When these parameters are not satisfactory for another part of the clip, another copy of the clip is put on another timeline track, and adjusted to satisfaction.

The final mix is done by cross fading among the many doctored segments or mixer channels. The segments may need to be adjusted to ensure the cross fading is seamless. More segments will be required to compensate for the pumping of the camera’s automatic volume control.

Using the Noise Gate

Though frowned upon by many, the noise gate can be very effective for reducing noise.

What the noise gate does is eliminate sound that is below a set threshold. One can also adjust the attack and release time of the action to minimize its side effects.

Earle very effectively eliminated a buzz in a phrase, without audibly affecting the voice quality. The following phrase was badly affected by the settings, and was corrected on another timeline track.

Substituting Background Noise

If we have a noise throughout most of a clip, its sudden absence, in the middle of the clip, can stick out like a sore thumb. You should always record a segment of only background noise for each clip, to be used later to fix such a situation. It is only a matter of adding a piece of this background noise back into the segment to eliminate the interruption. One could also use the background to add a needed break in the dialogue, provided of course that you had also shot some footage of the scene where the speaker’s lips were not on screen to switch the video to during the added audio “silence”.

Results

I was very impressed with the improvement of the sound clip after the operation. Most of the objectionable noise was totally removed, and the voice was strikingly more intelligible. The dialogue could now be followed effortlessly. While a clip that was originally very hard to follow was rescued, the final result certainly could not be called high quality audio.

Substituting Studio Sound

In practice well over 70% of the audio in high quality movies is generated in sound studios, rather than on set. All blue screen audio is done in post because of the risk of microphone shadows on the blue screen.

ADR (Automated Dialogue Replacement) replaces set recorded voice with voice recorded in a sound studio. Foley Recording and canned clips replaces the non-human sounds. And of course, music is written and recorded for the film. You could say that most high quality Hollywood movie sound is artificial sound.

ADR

There’s nothing automatic about Automated Dialogue Replacement, except that most studios automatically use it in their films.

The general principle is to repeat each phrase, recorded on set, in a loop. This loop is then played through the actor’s headsets, while the actors repeat the dialogue in sync and with the proper accent, emphasis and feeling. When one phrase has finally been done to the satisfaction of the dialogue director, the operation moves on to the next phrase.

The voices are recorded in a sound studio. If an intimate sound is needed, the actor is in very close proximity to the microphone. If a more distant voice sound is needed, the voice is recorded at normal distance, for best quality, and the characteristic of further distance is artificially achieved by appropriate tone manipulation and reverb.

Sound Effects

Non-human sounds recorded on set rarely sound realistic. You may have noticed that even AFV augments its amateur clips with sound effects. Fireworks and gun shots recorded on set never seem to sound right. The sounds of footsteps, doors, cars, birds, insects etc. are notoriously difficult to capture properly when they are central to the action.

Sound editors can spend a long time finding suitable sound effect clips to doctor until they sound right for the action on screen. I’ve listened to whole CDs worth of sound effects and found only one or two that I’ve found of marginally acceptable sound quality. There are a lot of sub-par sound effects available out there. The good ones, that are up to Hollywood standards, are rather expensive. Unfortunately, Hollywood quality is what we’re used to and expect.

Foley Recording

The introduction of radio and the talkies also introduced us to the sound effects man. He’s the guy who supplies all the non-human sounds using an array of devices to simulate creaky doors, footsteps on any surface, breaking glass, thunder, rain ... the works. The technique is named after Jack Foley, one of the original Hollywood sound effects men.

The best sound effects men can do a whole scene, in sync, on one take. Anyone remember Air Farce on CBC radio? The good sound effect man’s hardware and microphone placement has been proven to sound right. The good sound man is far more efficient than trying to find a suitable pre-recorded sound, and doctoring it to sound right and then synching it with the action.

Recording Your Own Sound Effects

Going out in the world to record a suitable sound can be a trying challenge. Look at all the lousy ones out there. George Lucas spent a long time finding the sound he wanted for the Star Wars light sabre. The classic sound of the light sabre is a recording of an impact on a set of old copper railway telegraph wires in their typical location on the tee bars of telegraph poles, struck under very specific high humidity conditions. You can hear the waves bouncing back and forth between the poles.

Getting suitable sound effects for surround sound Dolby 5.1 is another major hurdle for today’s quality directors. The Holophone family of surround sound microphones are widely used for ambient surround sound at sports events. The Holophone PortaMic 5.1 is intended for serious amateur use, with its ability to code Dolby 5.1 sound onto the standard stereo microphone inputs of camcorders. (Price in May 2010 under $600.)

It is a good idea to view the few good ones to inspire one and see just what can be done. Listen carefully to the products of producers that are on the cutting edge, like George Lucas and James Cameron.

Academy Awards for best sound are always an indication of the latest in sound quality.

In addition, some stars, like Tom Cruise seem to demand good sound for all his movies.