Here's a statement that may seem controversial: "When making videos, sound is more important than picture."
Studies show that while people will tolerate the worst quality video images, they will not watch programs that have poor quality audio. If you aren't convinced, look at this this way: nearly all of us have enjoyed television without actively watching the pictures (while cooking, for example); but no one can tolerate even a minute of TV viewing with the sound muted.
Room Tone and Ambient Sound
You will learn very quickly that, with a video camera, there is no such thing as silence. If you are filming indoors your camera will pick up what is known as 'room noise' - the hum created by electrical appliances (especially air conditioning units!), the buzz of fluorescent lights, the echo of sound waves bouncing off the walls (big rooms sound very different to little rooms), the noises of a building as it creaks gently around you.
Room noise is deadened by soft furnishing, so if you are seeking to minimize harsh sounds, film in a room with carpets, curtains and lots of soft cushions! You will need to take up the volume to compensate, however.
Outside there is also a lot of background noise, or ambient sound - passing traffic, birdsong, wind, nearby or distant people, aircraft, reversing trucks, squawking sirens - a whole cacophony of sounds that you cannot control. This is the noise of everyday life, and without it images begin to look very odd indeed. You therefore need to record it to add meaning to your video, but you need to take care that it is not too loud and that it does not drown out any vital dialogue or voice over. You have some control over volume levels when editing, but it is better to capture your sound effectively at source.
Dialogue or “Spoken To” Camera sound
There is a microphone on the front of your camera. Most home video cameras come with an omnidirectional microphone which basically records all the sounds that are present in front of the camera. This means that you must ensure that the dialogue you are trying to capture is much much louder than any background noise. More sophisticated camera models will also have an external mic jack where you can plug in a more powerful, directional microphone.
Recording human voices is perhaps the most difficulty-fraught area of working in video. Digital video cameras are reasonably good at coping with indoor levels of lighting, however, they are not good at recording sound and this is something you have to work around creatively, especially when interviewing a subject or recording dialogue.
Note - zooming the camera in on a subject does NOT also zoom the microphone.
Tips for good interview sound
Interview your subject in a quiet place (obvious, but often not done). Ensure that they sit as still as possible and are not fiddling with pens, paper etc that could cause unwanted noises.
Point the camera directly at them and place it as close as possible to them.
Plug a set of headphones into the camera to check what IT is recording, not what YOU are hearing.
Phrase your questions so that they should be obvious within the answers - your audience do not want to hear a disembodied voice answering questions, they want to hear the interviewee talking in as natural and flowing a way as possible. Think of your questions as prompts to get the interviewee to talk.
Remember that you will be cutting back and forth to your b-roll images, and that you can layer your interviewee's comments over different footage. You must prioritise getting good sound. If your interviewee stammers or stumbles over something, or if there is some unavoidable background noise (eg a telephone ringing) wait until the disturbance is over and roll the camera again.
The most efficient way to record a voice over is to find somewhere absolutely quiet (i.e. with very little room noise - see above) and speak directly into the camera microphone. You can record your own voice overs, or get someone else to act as the "voice" - think carefully about the gender, age and status of your "voice" - all of them will have implications for the meaning of your text.