Acoustic control by wave field synthesis

TLDR

Auditorium acoustics depend on direct sound and reflections, and electroacoustic corrections can introduce localization problems and artificial reverberant impressions. The study introduces electroacoustic wave‑front synthesis to avoid these side effects and aims to emit wave fronts that closely match real wave fields. Using the Kirchhoff–Helmholtz integral, stage source wave fields are measured, electronically extrapolated, and re‑emitted by loudspeaker arrays, with the image‑source concept enabling reflection synthesis so that generated fields can match real ones.

Abstract

The acoustics in auditoria are determined by the properties of both the direct sound and the later arriving reflections. If electroacoustic means are used to repair disturbing deficiencies in the acoustics, one has to cope with unfavorable side effects such as localization problems and artificial impressions of the reverberant field (electronic flavor). To avoid those side effects, the concept of electroacoustic wave front synthesis is introduced. The underlying theory is based on the Kirchhoff–Helmholtz integral. In this new concept the wave fields of the sound sources on stage are measured by directive microphones; next they are electronically extrapolated away from the stage, and finally they are re-emitted in the hall by one or more loudspeaker arrays. The proposed system aims at emitting wave fronts that are as close as possible to the real wave fields. Theoretically, there need not be any differences between the electronically generated wave fields and the real wave fields. By using the image source concept, reflections can be generated in the same way as direct sound.