It is challenging to characterize sound across space, especially in small enclosed volumes, using conventional microphone arrays. This study explores acousto-optic sensing methods to record the sound field throughout an enclosure, including regions close to a source and boundaries. The method uses a laser vibrometer to sense modulations of the refractive index in air, caused by the propagating sound pressure waves. Compared to microphone arrays, the sound field can be measured non-invasively and at high resolution which is particularly attractive at high frequencies, in enclosures of limited size or unfavorable mounting conditions for fixtures. We compensate for vibrations that contaminate and conceal the acousto-optic measurements and employ an image source model to also reconstruct early parts of the impulse response. The results demonstrate that acousto-optic measurements can enable the analysis of sound field in enclosed spaces non-invasively and with high resolution.
