Abstract: A pressure actuated noise attenuation device for an air induction system of an internal combustion engine is disclosed, comprising a quarter-wave tube and a tuning body movably mounted within the quarter-wave tube. The quarter-wave tube has an open first end in fluid communication with an air intake passage of the air induction system. The tuning body is movable by vacuum developed within the air induction system during operation of the internal combustion engine. The tuning body is also optionally acted upon by a biasing force and/or gravity. The tuning body is movable between at least a first position establishing a first operative length for the quarter-wave tube for attenuating air induction system noise at a frequency which is significant for a first engine operating level, to a second position corresponding to a second engine operating level.