Video Basics 2

Video Basics 2 - Sound

Poor sound quality makes an otherwise excellent video unwatchable. But we don’t generally have the time to re-record the audio in a clean studio environment and then synchronize it with the footage. To get a good sound recording in the field, here are some things to consider:

  • Principle #1: The built-in microphone on a video camera is pretty good – in a small room with lots of soft surfaces, no background noise, and no more than about 2 meters away from the person talking – assuming they have a good clear voice. Otherwise, use an external microphone. *Some consumer cameras do not have an external mic input. **Any time you plug in an external mic, also plug in headphones so you can hear what you’re getting.
    on camera mic distance
  • Principle #2: The closer to the sound source you can place the microphone, the better. Of course you can’t put it right in front of a person’s mouth, but you could put it just out of the shot above or below them. This is why clip-on (also called lavaliere) microphones are so popular. One of my favourite techniques is to tape a lavaliere mic to an existing podium mic, or to the podium itself, or a table near the front of the room. If the mic is very close to the sound source, then the background noise from the rest of the room is significantly reduced.
    close mic better
  • Principle #3: A directional mic (for example a shotgun mic) is very good at reducing the noise coming from behind it – but principle #2 still applies – closer is better.
    shotgun pattern
  • Principle #4: A hardwired mic will always sound better than a wireless mic – but sometimes you can’t run a mic cable back to your camera so you have to use wireless.
    wireless mic image
  • Principle #5: If you need to run multiple microphones then you need an audio mixer that is compatible with your camera’s microphone input. Professional cameras have XLR mic inputs that can usually be switched between mic level and line level inputs. Consumer cameras generally have only a 3.5mm stereo mic level input. There are mic adapters (Beachtek) that fit between the camera and the tripod to give you a couple of mic inputs and level controls.
    audio field mixer

Microphone types:

  • Dynamic mic – generally a handheld mic for rock and roll (Shure SM58 is the standard). Does not require battery or phantom power. Often used by an on-the-scene reporter. Works best about 4 inches from the person’s mouth.
  • Condensor mic – Uses a battery (or phantom power from the camera or mixer). Much more sensitive than a dynamic mic. Can be a clip-on (lavaliere) mic, or a camera-mounted, handheld, or pole-mounted shotgun mic, or a gooseneck podium mic, or a handheld or stand-mounted cardoid mic.

Pickup patterns:

  • Omnidirectional mics pick up sound from all directions. Many lavaliere mics are omni directional – which works fine because they are so close to the sound source.
  • Cardoid (heart-shaped) mics are much more sensitive to the sound in front of them than the sound behind them. Shotgun mics are hyper-cardoid.

Wireless microphones are generally lavaliere design. They consist of a microphone capsule that plugs into a battery-powered belt-pack transmitter. Then there’s a battery-powered receiver that plugs into the mic input on the camera. If you can set up near AC power, you can use an AC-powered receiver.

Selecting the right microphone depends very much on the situation you find yourself in. (see principles 1-5 above)

Exercise:
Make a series of 30-second recordings of a person talking at the front of the classroom using some of the following microphone setups, then compare the results (Advanced: try this outside, or in a noisy environment, or with two people talking)

  • on-camera microphone from the back of the room
  • on-camera microphone from the front of the room
  • hardwired lavaliere microphone clipped on the person talking
  • hardwired lavalier microphone taped to a table near the person talking
  • wireless lavaliere microphone
  • camera-mounted shotgun mic
  • dynamic mic on a stand near the person talking but just out of the shot