In this article are described the polar patterns of electro-dynamic microphones with two acoustical entrances. By definition the polar pattern is a ration between the microphone sensitivity when thita angle varies in related to the sensitivity when thita is 0 degrees when the frequency and the sound pressure are constant. It is well known that the reason for the proximity effect is the change of the wave front from a plane to a sphere when the distance to the sound source decreases. In this article we will define the relations of the polar pattern in a wave front with a sphere and plane form.
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