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The concept of the distance sensitivity (sometimes called "reach") of a microphone is an important one. The recordist must judge this microphone characteristic through acute listening and experience. The recordist must become aware of differences in timbre detail that are present between the miked sound source and the live sound source. Distance sensitivity is a microphone performance characteristic that is not included in the manufacturers specifications information, although it could be measured scientifically. Distance sensitivity is one that must be learned from experience and must be anticipated for the individual environment and recording conditions.
Many variables must be considered during the process of selecting and placing microphones. The primary variables for microphone selection were presented above. The variables of microphone placement will directly influence the selection of a microphone, even after an initial selection has been made. The placement of the microphone in relation to the sound source and the performance environment will greatly influence the sound quality of the recording. At times this influence may be as great as the selection the microphone itself.
The recordist must consider the following when deciding on the location of the microphone, in relation to the sound source:
• Distance relationships between the microphone, the
sound source, and the reflective surfaces of the environment
• Distance of the microphone from the sound source to be
recorded, and other sound sources in the environment
• Height and lateral position of the microphone in
relation to the sound source
• Angle of the microphone's axis to the sound source
• Performance characteristics of the microphone
selected, as altered by the above four considerations
Microphone placement interacts with microphone performance characteristics to create the recorded sound quality of the source: the distance of the microphone will be largely determined by the distance sensitivity of the microphone; the angle of the microphone will be largely determined by the frequency response of the microphone in relation to its polar pattern, the characteristics of how the sound source projects its sound, and the characteristics of the environment; the height of the microphone is also a result of the characteristics of the sound source, the environment, and the microphone's frequency response and distance sensitivity.
The sound characteristics of the environment in which the sound source is performing may or may not be captured in recording the sound source. The recordist may or may not wish to include them in the sound quality of the sound source. In either instance, the recordist must be in control of the indirect sound of the environment arriving at the microphone from reflective surfaces.
The recordist may seek to control the balance of direct and indirect sound. Through the selection and placement of a microphone with a suitable polar pattern and distance sensitivity, the desired characteristics of the environment may be captured, in the desired amount, along with the sound of the sound source. This will allow the recordist to record the sound of the sound source within its performance environment. The distance cues of the initial reflections in the early time field, and the amount of timbre detail, are evaluated by the recordist when deciding on the ratio of direct to indirect sound, and distance placement is adjusted accordingly.
The recordist's objective may be to capture the sound source without the cues of the environment. The sound source may be physically isolated (with gobos or in isolation booths) from other, unwanted sounds from the environment and other sources, or the leakage of unwanted sounds to the recording microphone might will be minimized with microphone pattern selection and microphone placement. This will allow the recordist the flexibility of being in complete control of the sound source; environmental characteristics are later applied to the sound through signal processing.
The sound of the environment will be controlled by the relationships of the microphone to the sound source, and any other sound sources that may be occurring simultaneously, including the sound of the environment itself.
The Reflective surfaces of the environment (or off any object in the environment) can cause the sound at the microphone to be unusable. Interference problems may be created when the sound from a reflective surface and the direct sound reach the microphone at comparable amplitudes. The slight time delay between the two sounds will cause certain frequencies to be out-of-phase (with cancellation of those frequencies) and certain frequencies to be in-phase (with reinforcement of those frequencies).
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