A touch sensor comprises a substrate capable of propagating acoustic waves and includes a first surface having a touch sensitive region. A first sidewall intersects the first surface along a first edge. The first edge is configured to propagate a first acoustic wave along the first edge. The first acoustic wave may be a one-dimensional edge wave. A wave converter converts the first acoustic wave to a second acoustic wave, and the first surface is configured to propagate the second acoustic wave across the touch sensitive region.