An assembly for an aircraft propulsion system, comprising: a first acoustic panel including a first perforated skin, a first non-perforated skin and a first cellular core arranged between and connected to the first perforated skin and the first non-perforated skin, the first perforated skin configured with a plurality of first perforations, and a first of the first perforations having a first width; a second acoustic panel including a second perforated skin, a second non-perforated skin and a second cellular core arranged between and connected to the second perforated skin and the second non-perforated skin, the second perforated skin configured with a plurality of second perforations, and a first of the second perforations having a second width that is smaller than the first width; and an inner barrel of a nacelle for the aircraft propulsion system, wherein the inner barrel comprises the first acoustic panel, wherein the first perforated skin has a first percentage of open area and the second perforated skin has a second percentage of open area that is less than the first percentage of open area, wherein each of the first perforations has the first width and each of the second perforations has the second width, wherein an adjacent pair of the first perforations is separated by a first distance and an adjacent pair of the second perforations is separated by a second distance that is greater than the first distance, wherein the first acoustic panel is located forward of the second acoustic panel along an axial centerline of the aircraft propulsion system, characterised in that the first distance is a distance between centers of the adjacent pair of the first perforations, and the second distance is a distance between centers of the adjacent pair of the second perforations. a first acoustic panel including a first perforated skin, a first non-perforated skin and a first cellular core arranged between and connected to the first perforated skin and the first non-perforated skin, the first perforated skin configured with a plurality of first perforations, and a first of the first perforations having a first width; a second acoustic panel including a second perforated skin, a second non-perforated skin and a second cellular core arranged between and connected to the second perforated skin and the second non-perforated skin, the second perforated skin configured with a plurality of second perforations, and a first of the second perforations having a second width that is smaller than the first width; and an inner barrel of a nacelle for the aircraft propulsion system, wherein the inner barrel comprises the first acoustic panel, wherein the first perforated skin has a first percentage of open area and the second perforated skin has a second percentage of open area that is less than the first percentage of open area, wherein each of the first perforations has the first width and each of the second perforations has the second width, wherein an adjacent pair of the first perforations is separated by a first distance and an adjacent pair of the second perforations is separated by a second distance that is greater than the first distance, wherein the first acoustic panel is located forward of the second acoustic panel along an axial centerline of the aircraft propulsion system, characterised in that the first distance is a distance between centers of the adjacent pair of the first perforations, and the second distance is a distance between centers of the adjacent pair of the second perforations.