The spatial information of a sound field in various kinds of halls has been measured and studied. Through these measurements, it is clear that not only early lateral reflections (which relate strongly to spatial impression [M. Barron, J. Sound Vib. 15(4), 475--494 (1971)] but also acoustic envelopment were some of the characteristics of the spatial information. Therefore, quantifying acoustic envelopment, and examining the influence of acoustic envelopment on spatial impression by performing experiments has been tried. The results are as follows: (1) Acoustic envelopment influences spatial impression, especially in regards to subjective envelopment; and (2) there is a possibility that subjective envelopment can be explained by the values (e, b, A.E.) that have been introduced in order to quantify acoustic envelopment.