Audio

Audio is an aspect of video production that is most often neglected, but is extremely important. 

There are many considerations when trying to get good audio, one of these is deciding what kind of mic will work best for the situation you're shooting in.

Most mics fall into two different categories:

dynamic	condenser
rugged	fragile
not temperature sensitive	temperature sensitive
no batteries	powered by batteries or phantom powered

Phantom powered means that the power for the mic comes from something thats plugged in, like a mixer (more on that later).

There are a lot of different types of microphone pick-up patterns (area around the mic that picks up sound).

These are some examples of microphone pick up patterns you might run into:

 

 

omni-directional mics: omni (all) vs. uni-directional: uni (one)

Omni-directional hand-held - these are rugged, general use mics that have an omni-directional pick-up pattern. These are good for man on the street interviews because they afford easy mobility, they are easy to share. But getting good sound depends heavily on talent and the way they hold the microphone. Background noise is common with hand-helds. Some hand-helds have a uni- (one) directional pick-up pattern.

This is a hand held mic:

 

Lavaliere mic (lapel or clip-on mics) - these omni-directional, condenser mics are great for sit down interviews when you dont want to get a lot of background noise. They are small and easy to hide. They let the talent have their hands free, but be careful, people like to play with the cord.

Shotgun mic - these are extremely sensitive, omni-directional condenser mics. They work well for picking up quiet sounds in a controlled environment, or sounds that are really far away. They are big, highly directional, extremely sensitive, and will pick up slightest handling noise. They work best when mounted on boom pole. If a mic is on a boom pole, be consistent with placement. If the mic is pointed in a different spot in different takes, your sound quality will change, sometime dramatically.

Microphone placement is very, very important as far as getting good sound.

      Bad                                      Good

Mixers

If you are using more then one mic, you want to use a mixer. Mixers take signals from several different sources and mixes them down into one signal. This allows you to control or adjust volume of each source and you can monitor the strength of your audio signal as it goes to tape.

Above is a picture of the front and the back of a portable mixer. The top half of the picture is the front, the knobs control the signal of each input, and theres a master knob that controls the overall volume . The bottom half of the picture is the back of the mixer, this is where you plug in the mics or other inputs.

A VU Meter is a visual tool to help you monitor the strength of your signal. Keep needle as close to 0dB as possible. When the needle is constantly in the red zone, your signal will be too strong and distorted or if the needle is too far to the left, your signal will be too weak or quiet. Wear headphones that are plugged into the camera, not the mixer, this way you can actually monitor what is going to tape.

When you are recording on a digital format, such as DAT or mini-disc, keep your levels BELOW 0dB ON DIGITAL RECORDERS, LEVELS ABOVE 0 WILL BE DISTORTED.

 

Line and Mic Level

Line level inputs are any inputs that are not microphones (tape decks, CD players, DAT decks, tuners, and most record players). Line levels are much stronger then Mic levels. The international standard level for line inputs is -10dBV for semi-pro and about +4dBV for pro equipment.

Balanced and Unbalanced Signals

You will notice that most mics have 3 pronged plugs on the end of the mic cords, these are called XLR plugs.

Many camcorders have mini mic inputs, the same size as your walkman headphones. In order to plug mics with XLR plugs into these camcorders, you will have to have an XLR to MINI audio cable.

A lot of higher end cameras may have XLR inputs, or adapters on the cameras that allow you to plug in mics with XLR plugs.

Signals that go through XLR cables are considered balanced. These signals are less prone to interference. XLR cables consist of three wires. One wire carries the audio signal; the second carries an inverted copy, and the third wire is the ground. When the signal reaches its destination, the inverted copy is flipped and added to the original. Any noise added by the wire is also inverted. When combined with the non-inverted noise, the two noise signals cancel each other out. Balanced signals are much better then unbalanced. Unbalanced signals go through one cable instead of 3, like the RCA cables you use to connect to your stereo or the 1/4 mini plug in most camcorders. An XLR to mini adapter will not change an unbalanced signal to a balanced signal.

Ambient Sound

Put simply, is the characteristics of the sound in a particular location. Silence is never silent, unless you live in a vacuum, thats why its always a good idea to record a minute or two of silence on your set. This will come in handy if you need to add a pause in your sound later. If you add a little of this room tone, the silence will sound more natural.

Final Thoughts on Audio

Its always a good idea to wear headphones when taping with an external mic - that way you are sure to get sound on the tape. In most cases, as soon as you plug a mic into the cameras mic input, you will disable the mic on the video camera.

Be safe, keep the power on your equipment off and keep your faders and master controls down when you are patching in orout of the camera or mixer. Its easy to ruin audio equipment with strong power surges.

Always try to get the best recording you can because its hard, if not impossible to fix it in post. Know how your stuff works ahead of time, the best way to learn about audio is to experiment. Play with your stuff before you try to make something.

Theres a lot more to know about audio, but there isnt room to go into all of it here. The best way to figure it out is to just do it.