# Reports

- Loudspeaker Directivity: On the Calculation of Full and Partial Directivity Indices

In the Loudspeaker Directivity survey being conducted at the 3D3A Lab, loudspeakers' directivities are determined through frequency response measurements taken along two orbits (horizontal and vertical) around each loudspeaker. In order to then compare the directivities of different loudspeakers, we use these measurements to compute various *directivity index spectra* which describe a loudspeaker's directivity either relative to the full sphere or to a given hemisphere, plane, or half-plane. In this document, we define these directivity index spectra and provide the relevant formulae needed to compute them.