Resonant transport enhancement by acoustic excitation in a sidewall-heated rectangular enclosure, in which natural convection flow is initially dominant, is considered. The enclosure is made of Plexiglas which dimensions are 30cm in height, 30cm in width and 30cm in depth. One sidewall of the enclosure is heated by an electrical foil heater and the other sidewall is maintained at a cold temperature by a cold water circulation. A woofer speaker is mounted on the bottom wall of the enclosure to generate pressure fluctuation inside the enclosure. All the walls of the enclosure are thermally insulated. The experimental results obtained indicate that there exists a resonant forcing frequency and velocity amplitude, which enhances thermal transport from the heated wall to the cold wall. It is also observed that, at the resonant state, the air temperatures inside the enclosure gather to an averaged air temperature by enhanced flow mixing. The relationship between the resonant frequency and the boundary layer wave along the vertical sidewall is discussed.