Abstract: 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.

Abstract: A vehicle cab noise suppressing system includes a cab interior panel having an opening exposed to acoustic noise in the cab, an acoustic resonator chamber, and a conduit communicating the resonator chamber to the opening. The resonator chamber is formed by a plurality of walls which are spaced apart from the interior panel and which are formed by a second panel. A third panel cooperates with the walls to enclose the resonator chamber. The chamber volume and the diameter and length of the conduit are chosen so as to acoustically tune the chamber to a noise frequency in the cab and thereby reduce noise in the cab.

Abstract: The invention relates to an exhaust pipe assembly. There is a need for an exhaust pipe assembly which transmits less noise to the environment. The exhaust pipe assembly includes a hollow exhaust pipe, and a hollow shield which surrounds at least a portion of the pipe. The shield is supported from and separated from the pipe by a plurality of elastomeric support elements which are interposed between the pipe and the shield. Each support element includes a larger body positioned between the pipe and the shield, and a smaller stem which projects from the body and extends into a bore formed in the shield. Each support element is preferably formed by injecting an elastomeric material through a corresponding one of the bores to form the body in the space between the pipe and the shield.