Spherical microphone arrays are widespread nowadays, especially with the advent of techniques for decomposing acoustic fields on the basis of spherical harmonics (i.e. Ambisonics). However, in these approaches, the corresponding arrays require a quadratically increasing number of microphones as the degree of the components to be estimated increases. However, for some applications, it is unnecessary to represent the whole solid angle of the sound field from the array point of view: for instance as soon as the array is placed near the boundaries of the acoustic field of study (i.e. walls in a room). To tackle this issue, one proposes a geometry which uses the acoustic rigid boundary condition at room walls to decrease the number of required microphones. With one eighth of a sphere array placed in the corner of a room, only certain spherical harmonics are required for the sound pressure field decomposition, and the microphone number can drop up to 8 times lower when compared to the full spherical array configuration. A microphone array prototype having the geometry of one eighth of a sphere is described, built, and evaluated in a rigid bounded eighth of an anechoic space.