Four-stroke internal combustion engine having reduced noise emissions

A four-stroke internal combustion engine having reduced noise emissions, the engine comprising:

• an engine housing including a cylinder;
• a piston adapted for reciprocating movement in the cylinder;
• an intake valve selectively movable to allow intake air into the cylinder;
• an exhaust valve selectively movable to allow exhaust gases to exit the cylinder;
• a filter element having
• a substantially flat inlet side;
• a substantially flat outlet side;
• a first housing portion;
• a second housing portion coupled to the first housing portion, the first housing portion and second housing portion defining an air chamber in which the filter element is supported, the second housing portion including
• an interior surface;
• at least one protrusion extending from the interior surface to space the inlet side of the filter element from the interior surface;
• and
• an air passageway including an inlet and an outlet, the outlet positioned adjacent the interior surface to deliver air to the air chamber between the interior surface and the inlet side of the filter element;
• wherein the at least one protrusion includes a wall at least partially defining the air passageway, and wherein the wall includes a curved outer surface having an apex that engages the inlet side of the filter element substantially in line contact.