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This paper describes a polydirectional microphone consisting of a single ribbon, the back of which is coupled to a damped folded pipe and an inertance in the form of an aperture. A single infinity of directional characteristics, ranging from bidirectional, through all variations of unidirectional to nondirectional, may be obtained by simply varying the size of the aperture.
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Harry F. Olson (1944) studied this question.
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