An acoustic insulation system (10; 100; 110) for an internal combustion engine mounted on a vehicle, the internal combustion engine including a cylinder block provided with a water jacket portion that covers a water jacket through which engine cooling water flows, and an oil pan that stores engine lubricating oil, the acoustic insulation system (10; 100; 110) comprising: an acoustic insulation cover (50; 102; 112; 120) configured to cover the internal combustion engine with a gap interposed between the acoustic insulation cover (50; 102; 112; 120) and the internal combustion engine; and a control device, wherein the acoustic insulation cover (50; 102; 112; 120) includes a cover front portion that faces forward of the vehicle, wherein the cover front portion includes: a plurality of inlets (62, 64; 126) for introducing outside air into an interior of the acoustic insulation cover (50; 102; 112; 120); and a plurality of inlet flaps (66, 68; 128); configured to respectively open and close the plurality of inlets (62;64;126) characterized in that: the plurality of inlets (62, 64; 126) includes a first inlet configured to introduce the outside air toward the water jacket portion and a second inlet configured to introduce the outside air toward the oil pan; and the plurality of inlet flaps (66; 128) include a first inlet flap (66; 128) configured to open and close the first inlet (62; 126) and a second inlet flap (68; 128) configured to open and close the second inlet (64; 126); wherein the control device is configured to control opening and closing of the plurality of inlet flaps (66, 68; 128) and to change the path of flow of the outside air by changing the opening and closing of the first and second inlet flaps (66, 68; 128) individually or collectively. an acoustic insulation cover (50; 102; 112; 120) configured to cover the internal combustion engine with a gap interposed between the acoustic insulation cover (50; 102; 112; 120) and the internal combustion engine; and a control device, wherein the acoustic insulation cover (50; 102; 112; 120) includes a cover front portion that faces forward of the vehicle, wherein the cover front portion includes: a plurality of inlets (62, 64; 126) for introducing outside air into an interior of the acoustic insulation cover (50; 102; 112; 120); and a plurality of inlet flaps (66, 68; 128); configured to respectively open and close the plurality of inlets (62;64;126) characterized in that: the plurality of inlets (62, 64; 126) includes a first inlet configured to introduce the outside air toward the water jacket portion and a second inlet configured to introduce the outside air toward the oil pan; and the plurality of inlet flaps (66; 128) include a first inlet flap (66; 128) configured to open and close the first inlet (62; 126) and a second inlet flap (68; 128) configured to open and close the second inlet (64; 126); wherein the control device is configured to control opening and closing of the plurality of inlet flaps (66, 68; 128) and to change the path of flow of the outside air by changing the opening and closing of the first and second inlet flaps (66, 68; 128) individually or collectively. a plurality of inlets (62, 64; 126) for introducing outside air into an interior of the acoustic insulation cover (50; 102; 112; 120); and a plurality of inlet flaps (66, 68; 128); configured to respectively open and close the plurality of inlets (62;64;126) characterized in that: the plurality of inlets (62, 64; 126) includes a first inlet configured to introduce the outside air toward the water jacket portion and a second inlet configured to introduce the outside air toward the oil pan; and the plurality of inlet flaps (66; 128) include a first inlet flap (66; 128) configured to open and close the first inlet (62; 126) and a second inlet flap (68; 128) configured to open and close the second inlet (64; 126); the plurality of inlets (62, 64; 126) includes a first inlet configured to introduce the outside air toward the water jacket portion and a second inlet configured to introduce the outside air toward the oil pan; and the plurality of inlet flaps (66; 128) include a first inlet flap (66; 128) configured to open and close the first inlet (62; 126) and a second inlet flap (68; 128) configured to open and close the second inlet (64; 126); wherein the control device is configured to control opening and closing of the plurality of inlet flaps (66, 68; 128) and to change the path of flow of the outside air by changing the opening and closing of the first and second inlet flaps (66, 68; 128) individually or collectively.