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Audio Density In Video

Scoring Series :: July 02, 2014

In today’s video scoring tip I’m going to be talking about the “density” of audio and how that affects your video or film and your filmmaking process.

When we talk about “density” in audio we mean how much aural or sonic space a dialogue track, sound effect, musical instrument, orchestra, etc., takes up in the available aural space. This is not volume (loudness) but represents the sonic “thickness” taken by that item. Some sounds are denser than others.

For example Alternating Current produces a sound that is 60 Hz. Machines, motors – even gasoline based engines - all produce this sound. If your film POV, whether dramatic, documentary or industrial, goes from outside a factory to inside, among the other clanging noises of whatever the machines are making, you will also have a low end 60 Hz hum in your audio track.

A 60 Hz motor is a very dense sound. It also happens to be in the same range as low strings, a suspenseful low-synthesizer drone and other low musical elements, which are also very dense. Not only do these sounds occupy the same frequency level, they both tend to be “big” – dense – commanding the attention of the audience. Obviously having a score with low, large musical elements in a scene with machinery or motors will create a muddy mess of your audio track. This is not limited to factories either – think cars, trucks, airplanes, lots of things will have 60 Hz sound or something near it.

Since the 60 Hz sound is driven by the presence of its source in your visual your only choice is to make sure the score does not have directly competing elements. Utilizing musical elements from the upper ranges (high strings, woodwinds, higher percussion, etc) would go a long way to creating a natural sonic balance that keeps your viewer focused on your content and story and not distracted by something they know is wrong but can’t quite put their finger on.

This issue isn’t limited just to large, low sounding sounds and musical instruments, it can be found throughout the audio spectrum. Another example that trips up a lot of small filmmakers is dialogue and narration – and mid-ranged musical instruments like guitar. Since using current pop and rock songs is quite common in contemporary filmmaking this issue comes up often.

An electric, rhythm guitar playing a chordal pattern is a very dense sound in the midrange of the audio spectrum. Not only is the human voice in the same range, it is a less dense sound, making it prone to being overwhelmed by most pop-rock music, even on tracks without vocals or where the vocals aren’t in at that moment. This often results in the entire pop-rock track being turned down in the video’s audio mix to make sure the dialogue is heard cleanly. The problem with that is by time the music track gets to that low of a level, it has lost all its punch and drive; everything that you liked about the track is now so soft as to be ineffectual and weak.

A much better solution would be to isolate the guitar part(s) and turn just those down. This allows you to keep the drums and bass, which typically won’t get in the way of the dialogue, much higher in the mix. Isolating just the musical elements that are denser than other elements is a great way to keep the energy and emotional impact of the music track while ensuring your dialogue is clearly heard.

These are only two examples of the impact of audio density on video and filmmaking. Becoming more aware of audio density will cause you to listen more carefully and find other ways that you have such audio conflicts – leading in time to much better and higher quality films.

Good filmmaking,

Kevin Klingler

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