Audio is a very important consideration when producing video files, whether they are produced with stock in mind, or for a blockbuster. Unfortunately audio is too often forgotten or given little priority when shooting video. No matter how dazzling the moving picture is, crappy audio will always devalue it.

With the advent of iStockAudio, we thought this would be a great time to address some of the issues around recording sound for video, and set some standards that will keep our collection at the top of the stock world.

First one must consider the audio source material that needs to be recorded. This is the first step in setting up your audio recording session. In this article we will be discussing how to capture three different types of audio sources.

  1. Vocal Narration
  2. On-Camera Dialogue
  3. On-Camera Environments

Vocal Narration

First one must consider the audio source material that needs to be recorded. This is the first step in setting up your audio recording session. In this article we will be discussing how to capture three different types of audio sources. Many times a dedicated vocal booth is used when recording narration. These small chambers prevent audio reflections and insulate against external environmental noises.

If you do not have access to a dedicated vocal both you can get similar results by controlling the audio environment with soft materials. For example placing blankets, insulation or heavy fabrics on all your hard surfaces in a room will go a long way to create an acoustically dead environment.

Because the recording is off camera, you have the luxury of placing the mic in close proximity to the sound source. Using a dedicated vocal mic such as a large diaphragm condenser mic, or a dedicated dynamic vocal mic is a popular choice when recording narration. Good vocal mics tend to provide a natural and full sound that is easy to distinguish from other sound elements included in the video project.

Most consumer cameras do not have the ability to properly record narration. A better choice is a standalone recorder or computer based system. More advanced cameras will usually do the trick too, but the camera will need to have the following features if you want to achieve a decent voice recording:

  • the ability to accept a mic signal (mic level)
  • the ability to provide phantom power to the mic
  • the ability to record to separate channels discretely
  • the ability to accept a standard XLR three pin mic cable
  • the ability to override the automatic level control (gain) through a manual setting.

On-Camera Dialogue

The challenge with recording on-camera dialogue is to capture only the sounds that are intended to be in the scene while rejecting other incidental sounds.

In these situations you may have only limited control over the sounds in the environment. Therefore choosing equipment and mic locations that capture as much of the desired dialogue as possible, while rejecting other sounds in the environment is essential. Although you should always try to eliminate as much unwanted sound as possible before you call for action, you can always improve a recording session by using equipment that selectively captures only the sounds you choose.

There are two mic types that do a great job in unpredictable acoustic environments. The first is the lapel mic. Also known as "lavaliere" mics, these miniature microphones are usually worn on clothing — clipped to a shirt, jacket or tie. They can also be worn under clothing, however this is not recommended as clothing usually muffles the sound or picks up the rustle of the clothing. Generally lapel mics are used in situations where it is okay to see the mic itself. The obvious advantage to a lapel mic is that it is very close to the subject's mouth. The primary disadvantage of this mic type is they usually pick up sound from all directions (omnidirectional), therefore they are not always useful outdoors and are easily swamped by loud background noises (machinery, vehicles, wind, etc).

The second mic type frequently used to capture on camera dialogue is the shotgun mic. The microphones themselves are a highly directional type called a "hypercardiod". These mics tend to reject sounds from the sides or back of the mic. A boom is a special microphone stand that allows the mic to be hung over the subject on camera. To keep the microphone out of the shot, these stands can be adjusted for height and angle. Shotgun mics have several advantages: They are highly directional, meaning that they only pick up sounds in the direction that they are pointing, rejecting other sounds. Also, because they are not connected to the actors there is no chance that an actor’s movements will create unwanted noise. Boom mics do have some disadvantages as they must be carefully positioned just outside the video frame, and many times a second person is needed to move the mic as a scene progresses.

At times a combination of lapel mics and shotgun/boom mics are used, and then mixed together later. This can give you the best of both worlds with the added benefit of having the ability to turn off one mic if you have unforeseen problems with background noise, or equipment failure.

The type of audio recorder will depend on the complexity of your setup. If your camera has the ability to accept a mic level then you may be able to use your camera as the recorder, eliminating the need to sync your audio later. However if your setup is more complicated or your camera does not accept a mic level, then an external recorder will be necessary. External recorders come in all shapes and sizes. There are dedicated video units that can record a few channels of audio, there are computer based systems, as well as stand-alone units that can accept 1 or 2 channels of audio to 30+ channels. The recorder you choose will be a combination of the scene complexity and your budget. However these are a few things to look for when choosing your recorder:

  • The recorder needs to accept a standard XPR mic cable.
  • The recorder needs to be able to connect all mics used in the scene.
  • The recorder needs to be able to sample at the same sampling rate as the camera to avoid sync problems in post production.
  • Most lapel & shotgun mics require phantom power, therefore the recorder will need to supply phantom power.
  • If the recorder can only record 1-2 channels of audio at a time then a mixer may be needed to mix all of the mic signals together before going into the recorder.

On-Camera Environments

It is important that a video scene sounds the same way it looks. For example if the footage shows vehicle traffic in the scene but no vehicles can be heard in the scene then the scene will be unconvincing. Likewise if actors talking in a large space sound like they are in a closet the scene will again be unconvincing.

To ensure that the room, or environment is acoustically represented in your footage it may be necessary to place additional microphones in the scene that attempt to pick up the relevant sounds in the environment. A good microphone type to capture environmental audio is an omnidirectional mic. An omni picks up sound in all directions creating an acoustical picture of the environment or room. Generally speaking 2 environmental mics will do an excellent job of creating a stereo sound stage. The two most common mic techniques are the x/y or a/b mic placement patterns. The a/b mic pattern uses two mics placed in different locations each picking up elements of an environment. The advantage in using this technique is a very wide and convincing stereo field, however its disadvantage is potential phase cancellation where a sound reaches each mic at a different time and cancels each other out.

A simpler solution is to use cardiod pattern mics in the x/y technique, where the two mics are placed very close together but are pointed in different directions, picking up a slightly different soundscape but avoiding any phase cancelation.

If your on camera mic is of very high quality it may be up to the task of capturing the sounds in a scene, however to frame a shot, the camera placement is usually too far from the subject to record good sound. This is especially true if the camera needs to be moved or handled during the shot. The best solution is to use external mics connected to the camera or a standalone recorder. The recorder should have these features as a minimum:

  • The capability of accepting a mic signal (mic level).
  • The capability to provide phantom power.
  • The capability to record a minimum of two channels of audio.
  • The capability to accept standard XLR three pin mic cables.

A video project where time and effort have gone into the audio design will produce a final product that is far more convincing than if you were to simply use the low quality mics attached to your camera. Great audio takes some careful attention to details, but done properly your project will have that extra level of sophistication that separates yours from the rest.

One final word about audio for video, specifically for Videographers: for the past couple of years we have encouraged people to submit video without any audio if the original audio quality was poor. We still believe this is the best option if the audio recording is distracting. However, audio is very easy to strip off a video file, and many customers do that anyway, unless the sound is critical to the image. So, although we prefer the video to have good audio, we will generally not reject a video for having record levels that are too low, mic handling sound etc UNLESS the sound is: obnoxious over the top loud; unrelated completely to the picture; voices not synced to a person in the shot (off camera direction etc); or music.


Image credits:
Microphone: Your attention please! by jacomstephens
RadioTalkShow and NewsMakers by A-Digit
Small microphone by proxyminder
Interview by track5


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