Reflection and transmission of acoustic and entropy perturbations interacting with steady subsonic fronts separating cold and hot phases are studied in one-dimensional planar geometry. The dynamics of such fronts is governed by radiative cooling and heating and thermal conductivity. The fronts are found to be evolutionarily stable. It is shown that at small Mach numbers of the front, M < 0.01, acoustic energy can be partly absorbed by the cooling-conductive interface. In the interval of Mach numbers M ~ 0.01-0.3 the transmission coefficient is found to be larger than one, i.e., the transmitted energy flux is enhanced in comparison with the energy flux falling onto the interface. The reflection coefficient exceeds one in a wider interval of Mach numbers, M ~ 0.01-0.8, so that at 0.01 < M < 0.8 the total energy flux scattered by the cooling-conductive interface is larger than the flux falling onto it, and thus such interfaces amplify acoustic energy. It is shown also that entropy perturbations coming onto the front from the hot phase can generate sound waves behind the front. Possible implication of such amplification of acoustic motions as a source of turbulence in interstellar molecular clouds with the lack of star formation is discussed. The energy density of sound perturbations in the intercloud gas of the ISM is argued to be high enough to replenish dissipation of mechanical energy in molecular clouds.