DAGA 2010 - Deutsche Gesellschaft für Akustik eV

222 DAGA 2010 Programm
Open spherical microphone arrays with omnidirectional capsules do not
allow for full spatial capture at some frequencies. In contrast, rigid sphere
arrays exploit diffraction to overcome this limitation, however they impose
a challenge in filter design. Alternatively, literature suggests opensphere
designs using cardioid capsules to have less demanding requirements.
However, their performance is degraded if non-negligible acoustic
obstacles like construction hardware are introduced.
This paper presents a unified description of open microphone arrays
enclosing a concentric rigid spherical scatterer of variable size. As frequency
range and spatial resolution impose conflicting demands, this
study intends to improve the understanding of spherical array designs.
Diffraction effects and different microphone patterns are simulated and
allow a discussion of various array layouts. In particular, the presented
results outline the influence of imperfections such as noise and physical
and electrical misalignment on an array’s performance.
Mi. 17:45 Bauwesen H2 Virtuelle Akustik I
Microphone Arrays Utilizing Rigid Cones for Sound-Field Analysis
H. Pomberger
Institut für Elektronische Musik und Akustik, KU Graz
Analysis and acoustic imaging of 3D sound-fields is a fascinating issue
in emerging applications of microphone arrays. In particular, cylindrical,
spherical, and planar microphone arrays have been considered as suitable
geometries, each of which uses microphones placed along a coordinate
surface of the associated coordinate system. The array surfaces
separate two domains, i.e. inside or outside of spherical/cylindrical surfaces,
or both half spaces of a planar coordinate system. Most arrays use
only pressure microphones, which introduces possible confusion between
the domains separated by the array. To avoid this confusion rigid
arrays can be used, i.e. microphone arrangements on sound-reflecting
surfaces. The cone is a further coordinate surface in spherical coordinates,
however, it has not been utilized as surface for rigid microphone
arrays so far. This paper investigates whether the use of rigid cones as
diffraction objects is beneficial for sound-field analysis with microphone
arrays. Acoustic diffraction by an infinite rigid cone is easy to describe by
imposing a boundary condition to the wave equation, however, practical
issues imply cones of finite length. Thus the influence of the cone length
on the acoustic field is crucial for applications and will be explored.