An air pump assembly includes a pump module having an outer surface and a casing at least partially surrounding the pump module. The casing has an inner surface defining a cavity sized to snugly receive the pump module such that the outer surface of the pump module is in substantial engagement with the inner surface of the casing and is substantially prevented from moving with respect to the casing when the pump module is received within the cavity. At least one airflow passageway is defined between the inner surface of the casing and the outer surface of the pump module. The airflow passageway is configured so that air flowing through the passageway changes direction at least one time to reduce the transmission of noise from the air pump assembly.