ABSTRACTPoint source reflection/transmission responses from planar interfaces based on the Sommerfeld‐Weyl integral are causal and are given in the form of a solution integral with an infinite integration limit. They can be simply transformed to integrals with a finite limit by an approach that takes into account causality as well as time‐symmetry aspects. To introduce the fundamental principles involved, the transformation is applied to the simple case of a point‐source response from a planar acoustic interface. For a point source above a planar interface separating an upper and lower acoustic half‐space of velocityc1andc2the inhomogeneous plane waves in the Sommerfeld‐Weyl source representation do not contribute to the final result ifc1≤c2and only a limited spectrum of inhomogeneous plane waves comes into