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Wayne State University

Aim Higher

Dec 6 / Darryl Shreve

The Nuts and Bolts of Sound for Video

Spoiler alert, your head may explode from reading this blog.

Sounds are vibrations. They can travel through the air, water or other mediums.  People that create videos or music use devices to capture the sound and then place it into a new medium, like a movie or an audio CD.

Lets simplify it even more. Someone sings and the sound goes into an ear. Now let’s get more complicated.

Sound can be captured into a device that records audio. It can be recorded with the video or separately into a field unit and then synced later. The recording source could be a camera, a field recorder or a computer.

This gets even more complicated when trying to get the best sound. There are many pieces of equipment to choose from offering different types of services. Note the diagram below for one such scenario.

Your expertise with each device will determine your success rate on shoots. Below are a few types of audio gear that are commonly used with productions.

 

MICROPHONES – Audio is transmitted using one of these devices.

 

MIXERS – You can mix several different audio sources into one (mono) or two (Stereo) audio channels and then send it back out to a record source or speakers.

 

COMPRESSORS/LIMITERS and AUDIO EFFECTS UNITS – Applies effects to an audio signal. Can be configured different ways, but usually a signal is sent from a mixer to the unit and then back into the mixer before finally going out to the record source and/or speakers.

 

FIELD RECORDER – Records audio only and is synced later with the video.

Again,  sound is a vibration and its sound wave is often represented by a sine curve.

I sense your head is starting to hurt now. Well, the diagram below probably won’t help with that. It illustrates what a sound wave looks like. Amplitude has to do with the height of a wave and frequency has to do with how frequent the wave occurs in a second.

As the oscillation (revolution of the s-curve) of a frequency increases in one second, so does the pitch. The amplitude signifies loudness.

If we look at how other creatures communicate it might make more sense. A whale sings, a dolphin clicks and a cat meows. All at different frequencies and amplitudes. Researchers have discovered that these songs or clicks are instrumental in the identification of other animals and organized foraging of food. These vibrations of communication are not just limited to mammals, look at butterflies, caterpillars and ants. Maybe those Disney and Pixar movies with the talking animals and insects aren’t too far off after all.  Vibrations at selective frequencies play a key role in how we all communicate (and yes, I have been told that I spend too much time watching the discovery channel).

So when thinking about sound, understand that what you are really hearing is a series of vibrations, much like the exploding of heads from reading all of this “geek speak”, but hey….I did warn you.

Just saying.

Production tips for good sound:
-Set analogue audio sources to 0dBs on the audio meters. Meaning, the bulk of the audio should rest at 0, but can peek a few decibels higher.
-Set digital audio sources to -12dBs on the audio meters for broadcast sources.
-Set digital audio sources to -6dBs on the audio meters for Internet sources.
-Never record anything without using headphones attached to the record source.
-Treat sound like an object and use it to create depth.
-Your film score (music bed) and sound effects are two different things, but they work together as the score to ground your video.
-Try to keep your mic about 8 inches from your subject’s mouth.
-Use windscreens and “socks” when outside. (Cuts down on wind noise)