An air intake tract with a hydrocarbon adsorber is provided for adsorbing hydrocarbons of a motor vehicle. The hydrocarbon adsorber includes at least one first layer constructed of a hydrocarbon adsorbing material. Optionally, one or more stacked layers are provided including at least an uppermost layer and at least one intermediate layer. The at least one first layer includes a solid shape within an outer boundary and is adapted for sonic welding onto an interior of the air intake tract. The uppermost layer and any intermediate layers include an opening such that the uppermost layer provides access for a sonic welding tool from an upper side of the subassembly to the at least one first layer through the opening.