A sound dampening assembly adapted to engage an exhaust pipe in an automotive engine exhaust system adjacent an outlet of an internal combustion engine. The assembly includes a bottle portion having a single opening and an interior defining a predetermined amount of volume and a neck portion having a first end attached to the opening of the bottle portion and extending from the bottle portion. The neck portion is in fluid communication with the bottle portion interior and includes a second end adapted to be attached to the exhaust pipe. The neck portion has an interior defining a predetermined amount of volume and the bottle portion and the neck portion are sized to attenuate vibration at a predetermined frequency in the exhaust system.