The geometry of the microphone surrounding a transducer capsule has a large influence on the acoustical behaviour of the transducer as a whole. Therefore, only 4 microphone design principles are in common use today: with mostly free-standing capsules; with cylindrical housings; embedded in large boundary layers; or with spherical housings. Especially for omnidirectional pressure transducers, the spherical housing can be applied, yielding positive results on frequency response and polar pattern. Spherical housings have been investigated, and introduced to microphone design some 50 years ago. An overview of the historical development, and their applications shall be presented as well, leading to the current embodiments of this principle.
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