A joint inversion of phase velocity and H/V ratio curves, both obtained from seismic-noise recordings, permits the retrieval of the shear-wave velocity structure of local sedimentary cover. Our inversion scheme uses a genetic algorithm and considers the influence of higher modes on the data sets. Encouraged by the results published previously on joint inversion (Parolai et al., 2005) we went one step further. We found, using a synthetic data set, that the impedance contrast at the sediment-bedrock interface has a strong influence on the shape of the H/V ratio curve, which therefore allows the bedrock S-wave velocity to be well constrained in the joint-inversion procedure. Our observations were further confirmed using a real data set.