1. A method of reconstructing a sound field, the sound field being generated by at least one sound source, the method comprising: receiving a set of measured values of at least a first acoustic quantity measured at respective ones of a set of measurement locations; computing each of a set of correlation functions, each correlation function being indicative of a correlation, in a spatial domain, of at least one set of plane waves at a first one of said measurement locations with the at least one set of plane waves at a second location computing a second acoustic quantity indicative of the reconstructed sound field at a target location from at least the computed correlation functions and the set of measured values; and wherein the method further comprises storing a representation of a set of interpolation functions for interpolating respective contributions to the correlation functions, the set of interpolation functions including one or more two-dimensional interpolation functions, each contribution being a function of two or less input parameters; and wherein the computing each of the set of correlation functions comprises computing each correlation function as a linear combination of values obtained from the stored representation.