Abstract: A resonator includes an inner perforated tube, an outer shell, and a plurality of annular ribs extending radially therebetween and defining resonant chambers. Progressive stepping of ribs and grooves enables axial insertion assembly with minimal cost. The need for welding or secondary bonding operations is eliminated.

Abstract: A filter includes first and second axially spaced end caps having filter media extending axially between the end caps and extending in a closed-loop around a perimeter defining a hollow interior communicating with an axial flow opening through one of the end caps. One or more columns extend axially in the hollow interior between the end caps and are laterally spaced from the axial flow opening and have hollow sub-interiors for receiving one or more posts extending axially thereinto from a base for mounting the filter to the base in axial compression and with a wiper seal.