Perturbation to the cyclic oscillation frequencies δν^c = (2π)^-1δω, induced by the sound speed perturbation at the edge of the core, as predicted by Eq. (3). Shown are the results for the two models considered in Fig. 2 and an additional model of the same mass with an intermediate age of 3.25 Gyr. The dotted-dashed lines show linear fits to the perturbations to the 10 modes of higher radial order.