A 256-microphone measurement system to estimate 3d directivity patterns
Résumé
The first published attempt to measure human voice directivity in 1929 involved a single microphone and a rotating chair. Since then, a number of experiments were conducted, increasing the level of detail of the sound field representation according to the available equipment. Most experiments assumed repeatability of voice production by the human talker over an iterative process, which can hardly be guaranteed even for trained subjects. Hence using a rotating device to retrieve the 3D directivity of a human talker is questioned. All measurement positions should preferably be recorded simultaneously to ensure an optimal consistency of the obtained directivity patterns. The present experimental setup is composed of 256 MEMS microphones located on a spherical structure of 1.80 m radius. The characteristics (sensitivity, frequency range, and dynamics) of those compact devices are presented and allow for measurements of voice directivity from 50 Hz up to 20 kHz. A first step of characterization is conducted with a reproducible sound source composed of 12 Aurasound loudspeakers producing controlled directivity. Then, human talkers are recorded in the system. Far-field directivity functions are estimated using a spherical wave propagation model. The obtained results are consistent with the previous literature and provide an extended angular accuracy.
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