This paper describes theoretical and experimental studies on the sound field around a vibrating rectangular solid enclosure. In the computation, it is assumed that the effects of diffraction and reflection of sound can be neglected, and that the vibration of each plate of the enclosure can be expressed approximately by using the normal function of a rectangular plate with simple support along all edges or the composite normal function by the product of those of two clamped beams perpendicularly intersecting each other. The sound pressurelevel distribution has been measured in more detail with the sound visualizing device built as a trial. The results obtained are as follows: (1) The diffraction effect is small in the field near each surface of the enclosure and the computation can be applied to a plate in the first mode vibration but not in the higher mode vibration. (2) The composite normal function holds to a fairly good approximation and experimental values agree well with computed results. (3) The state of a sound field like sound pressure level distribution can be grasped in detail by the sound visualizing method.