FIG. T-17. The tuning effect illustrated for a wedge; the material above and below it is the same, but the wedge has different acoustic impedance. When the wedge is a quarter-wavelength (1/4) thick, the second half-cycle of the reflection from the top interferes constructively with the first half-cycle from the bottom, resulting in an increase in amplitude. The magnitude of the increase and how many amplitude maxima there are depend on the shape of the embedded wavelet. (a) The wedge; (b) seismic section across a linear wedge that has lower acoustic impedance than the surrounding sediments for a minimum-phase wavelet; (c) amplitude versus thickness graph.