A resonator attenuates sound waves at first and second frequencies. The resonator includes a first tube, and a second tube received within the first tube. Both tubes have an open end and a closed end. The first tube has an axial length which is longer than the axial length of the second tube. The first tube attenuates sound waves at the first frequency and the second tube attenuates sound waves at the second frequency. The second tube has an outer wall which engages an inner wall of the first tube. The open end of the second tube is surrounded by the open end of the first tube. The open end of the first tube is attached to an engine air intake conduit. The conduit communicates air from a charge air cooler to an engine intake manifold.