In many ways , recording audio on location is a bigger challenge that the facilities available in a purpose built studio. There are often problems that are created simply by lack of time, equipment limitations and the productions convention that sound follows picture. It is rare that good sound conditions are decided on before the selection of the shot and yet sound and image are often of equal importance and need equal attention. It is far easier to fix it at the recording stage than to endeavour an impossible task of carrying out remedial work at the edit.
Auto-gain can be considered the equivalent of auto-iris and needs to be used with the same degree of caution. Auto-gain will respond to rapid increases of sound intensity by rapid reduction of the recording level, and this is often undesirable. Problems can occur when recording speaking with low background noise and the auto-gain adjusts for the correct level. When speech pauses the level increases the background noise. This causes an unpleasant effect. Use auto gain when there is not opportunity to take a sound level check before recording. Decide whether auto-gain will cause more problems than it will solve.
Manual control allows intelligent decisions to be made about the levels and will rely on the built in limiter (if there is one) to take care of the unexpected sound.
The major for outside location is wind noise. Most microphone manufactures produce windshields for their products in the shape of foam covers. Lapel or personal microphones suffer badly for wind noise, and their small windshield provides little assistance. Purpose built windjammers can assist in this area, but can not obviate it entirely.
Take care in the positioning, by ensuring that it is not likely to rub on clothing as the speaker moves.
On location there is often unwanted background noise. Try to put the speakers back towards the noise so it acts as an acoustic shield for the unwanted sound.
Monitoring audio quality is difficult for a single camera operator. If there is time a double-sided head set can be used to check quality, but more often time is at a premium. An audio check prior to recording can assist in adjusting levels prior to the final take. It is only by listening to the sound that an evaluation can be made. Audio meters only evaluate the level of sound not the quality. The least you can do is by using the audio meters intelligently by ensuring overload does not occur, as beyond this point distortion will occur. Once distortion is recorded nothing can be done in post-production to alleviate it. Decide whether auto-gain will cause more problems than it will solve.
Recording an interview on one microphone
When recording an interview with the presenter holding one hand held microphone, always listen to establish who has the prominent voice and get the presenter to favour the microphone towards the quieter of the two. The problem arises when the interviewer is consistently moving the microphone form one to the other and varies the distance. If they are incorrect in these distances the result will be worse than not moving the microphone at all.
Pieces to camera
Probably the first choice for a shot of a presenter talking straight to the lens is to rig a radio microphone, A piece to camera can also be accomplished by using a rifle microphone protected from the wind mounted on the camera providing the camera does not pane away from the speaker. If the shot is tighter than a medium close up a stick microphone can be held by the presenter just out of shot.
Recording an interview on two microphones
Route each microphone to a separate channel (split-track recording)
- Connect interviewee’s microphone to either channel 1 or 2 (opposite channel to second microphone) and set level
- Connect interviewer’s microphone to either channel 1 or 2 (opposite channel to second microphone) and set level
If two persons are close together and separately miked, it is possible, if one of them has a much louder voice than the other, to pick up the loudest voice on both microphones. This causes phase cancellation to the recorded sound because of the time delay due to the distance between the persons. This can be avoided if each microphone level is only set at the correct level when the people are talking. Therefore test levels need to be taken and settings made prior to the start of filming.
- Just as continuity of skin tone exposure is required for the presenter, so continuity of audio quality is required for their voice throughout the production. Try to be consistent not only with video but also audio.
- Poor acoustics (echo, boxy sound) can be partly overcome with close microphone techniques. They impart an identifiable quality to the voice and need to be maintained for the whole of the item.
- To avoid distraction and problems in editing, background sounds such as air –conditioners, refrigerators, telephones may need to be switched off.
- Highly directional microphones are not always the solution to poor separation between voice and background noise. They can still pick up traffic noise, aircraft, working machinery, etc., because often their directional ability is restricted to voices and higher frequencies.
- The ear/brain can filter out and ignore general ambient sound and concentrate on the audio source which is the subject of their attention (e.g. One voice in a crowd). Microphones have limited selection and no priorities in content selection.