A housing of plastics material for a centrifugal blower for automotive HVAC systems, having a base end wall, a cover end wall and a side wall extending between the base end wall and the cover end wall, in said housing there being defined an impeller chamber and an air outlet duct, wherein on the cover end wall there is formed an air inlet opening facing the impeller chamber, and on the side wall there is formed an air outlet opening facing the air outlet duct, wherein a sound absorption structure is arranged on said side wall, said sound absorption structure comprising at least one resonant cavity (42, 52) fluidically connected to the impeller chamber and the air outlet duct through a plurality of slits (41, 51) arranged on the side wall and facing at least one of said impeller chamber and air outlet duct, characterized by comprising a base half shell formed by the base end wall and by a first portion of the side wall, protruding from the base end wall, said first portion of the side wall surrounding the impeller chamber and delimiting on a radially outer side the air outlet duct, a cover half shell formed by the cover end wall and by a second portion of the side wall, protruding from the cover end wall, said second portion of the side wall delimiting on a radially inner side the air outlet duct, and at least one of: - a chamber side panel fitted in a seat formed in the base half shell and facing said impeller chamber, wherein said at least one resonant cavity is formed between the chamber side panel and said first portion of the side wall, and wherein said slits are formed on the chamber side panel, and - an outlet side panel fitted in a seat formed in the cover half shell and facing said air outlet duct, wherein said at least one resonant cavity is formed between the outlet side panel and said second portion of the side wall, and wherein said slits are formed on the outlet side panel, wherein the base half shell and the cover half shell are joined to each other. wherein a sound absorption structure is arranged on said side wall, said sound absorption structure comprising at least one resonant cavity (42, 52) fluidically connected to the impeller chamber and the air outlet duct through a plurality of slits (41, 51) arranged on the side wall and facing at least one of said impeller chamber and air outlet duct, characterized by comprising a base half shell formed by the base end wall and by a first portion of the side wall, protruding from the base end wall, said first portion of the side wall surrounding the impeller chamber and delimiting on a radially outer side the air outlet duct, a cover half shell formed by the cover end wall and by a second portion of the side wall, protruding from the cover end wall, said second portion of the side wall delimiting on a radially inner side the air outlet duct, and at least one of: - a chamber side panel fitted in a seat formed in the base half shell and facing said impeller chamber, wherein said at least one resonant cavity is formed between the chamber side panel and said first portion of the side wall, and wherein said slits are formed on the chamber side panel, and - an outlet side panel fitted in a seat formed in the cover half shell and facing said air outlet duct, wherein said at least one resonant cavity is formed between the outlet side panel and said second portion of the side wall, and wherein said slits are formed on the outlet side panel, - a chamber side panel fitted in a seat formed in the base half shell and facing said impeller chamber, wherein said at least one resonant cavity is formed between the chamber side panel and said first portion of the side wall, and wherein said slits are formed on the chamber side panel, and - an outlet side panel fitted in a seat formed in the cover half shell and facing said air outlet duct, wherein said at least one resonant cavity is formed between the outlet side panel and said second portion of the side wall, and wherein said slits are formed on the outlet side panel, wherein the base half shell and the cover half shell are joined to each other.