Spatial sound field recording and reproduction in reverberant rooms require the measurement of room transfer functions (RTF) followed by room equalization to correct undesired reflections. Typically, the RTF rapidly varies over the room and hence requires an infinite number of point to point measurements to characterize the room. This paper provides a modal based parameterization of the two dimensional acoustic transfer function over a sizeable spatial region in which the source(s) lie and a sizeable spatial region in which the receiver(s) are located. As a result, a finite set of modal coefficients is shown to be capable of predicting the RTF between any two arbitrary points from the aforementioned source and receiver regions.