## Idea for Sign-Change Retrieval in Magnitude Directivity Patterns

* Presenting author

Abstract:
This contribution deals with an idea to insert potential sign-changes in three dimensional magnitude directivity measurements to simplify their global interpolation in terms of spherical harmonics. Directivity patterns, e.g. of musical instruments, are often measured on a grid of spherically surrounding directions. While the magnitude is most reliable and carries the most essential information, phase can be error-prone and irrelevant, especially at high frequenices. Disposal of the phase often reduces potential destructive interference due to poor centering, spatial sampling, etc.In such cases, the resulting all-positive zero-phase pattern is probably the most simple representation of the directivity not only for an accurate local interpolation using three neighboring measurement nodes, but for global interpolation using spherical harmonics.However, accurracy suffers for some particularly simple patterns such as the first-order dipole pattern. While it might be acceptable that after disposing the phase local interpolation just cannot reconstruct the zeros, a global interpolation using low-order spherical harmonics decomposition gets inaccurate everywhere.Here, we assume that directivity patterns should be of uniform phase everywhere, except between the connected regions associated with different directional peaks, where a potential sign change should be investigated. Our contribution tests the idea in a simulation study with some examples.