In this article we discuss the proximity effect of electro-dynamic microphones with two acoustical entrances. The proximity effect is appearing when a directed microphone is getting closer to the sound source. It is described as a alteration of the frequency response and more specifically as an increase of the microphone's sensitivity when the distance is decreasing. The reason for this change is the change of form of the sound wave from a plane to a sphere when the distance to the sound source is decreasing. The goal of this article is to determine the relationship of the proximity effect from the angle between the sound wave and the acoustical axis of the microphone.
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