In sound engineering, as opposed to communications which will not be considered here, there are commonly considered to be three classes of sound: speech or dialogue, music and effects. Each has its own considerations and requirements regarding the use of microphones.
There are a number of scenarios where speech may be recorded, broadcast or amplified:
- Audio book
- Radio presentation, interview or discussion
- Television presentation, interview or discussion
- News reporting
- Sports commentary
- Film and television drama
In some of these, the requirement is for speech that is as natural as possible. In an ideal world perhaps it should even sound as though a real person were in the same room. The audio book is in this category, as are many radio programs. There is a qualification however on the term 'natural’. Sometimes what we regard as a natural sound is the sound that we expect to hear via a loudspeaker, not the real acoustic sound of the human voice. We have all been conditioned to expect a certain quality of sound from our stereos, hifis, radio and television receivers, and when we get it, it sounds natural, even if it isn’t in objective terms. In the recording and most types of broadcasting of speech there are some definite requirements:
- No pops on 'P’ or 'B’ sounds.
- No breath noise or 'blasting’
- Little room ambience or reverberation
- A pleasing tone of voice
Popping and blasting can be prevented in two ways. One is to position the microphone so that it points at the mouth, but is out of the direct line of fire of the breath. So often we see microphones used actually in the line of fire of the breath that it seems as though it is simply the 'correct’ way to use a microphone. It can be for public address, but it isn’t for broadcasting or recording. The other way is to use a pop shield. Ideally this is an open mesh stocking-type material stretched over a metal or plastic hoop. This can be positioned between the mouth and the microphone and is surprisingly effective in absorbing potential pops and blasts. Sometimes a foam windshield of the type that slips over the end of the microphone is used for this purpose. A windshield is really what it says, and is not 100% effective for pops, although its unobtrusiveness visually has value, for example, for a radio discussion where hoop-type pop shields would mar face-to-face visual communication among the participants.
The requirement for little room ambience or reverberation is handled by placing the microphone quite close to the mouth – around 30 to 40 cm. If the studio is acoustically treated, this will work fine. Special acoustic tables are also available which absorb rather than reflect sound from their surface.
'A pleasing tone of voice’? Well, first choose your voice talent. Second, it is a fact that some microphones flatter the voice. Some work particularly well for speech, and there are some classic models such as the Electrovoice RE20 that are commonly seen in this application. Generally, one would be looking for a large-diaphragm capacitor microphone, or a quality dynamic microphone for natural or pleasing speech for audio books or radio broadcasting.
In television broadcasting, one essential requirement is the microphone should be out of shot or unobtrusive. The usual combination for a news anchor, for example, is to have a miniature microphone attached to the clothing in the chest area, backed up by a conventional mic on a desk stand. Often the conventional mic is held on stand-by to be brought on quickly if the miniature mic fails, as they are prone to through constant handling. Oddly enough, the use of microphones on television varies according to geography. In France for example, it is quite common for a television presenter to hand hold a microphone very close to the mouth. Even a discussion can take place with three or four people each holding a microphone. The resultant sound quality is in accordance with French subjective requirements. Radio microphones are commonly used in television to give freedom of movement and also freedom from cables on the floor, leaving plenty of free space for the cameras to roll around smoothly.