System and method for attenuating sound in a gas turbine engine

An exhaust section of an aircraft engine, comprising:

• an exhaust case extending along a central longitudinal axis, the exhaust case having an exhaust inlet receiving an exhaust flow of the aircraft engine and an exhaust outlet exhausting the exhaust flow;
• and
• an annular body disposed in the exhaust case and exposed to the exhaust flow, the annular body having a radially outer sheet, a radially inner sheet, an annular cavity defined between the radially outer sheet and the radially inner sheet, one or more plates disposed in the annular body and subdividing the annular cavity into sub-cavities, one or more holes disposed through the radially outer sheet, the one or more holes configured for transmitting acoustic pressure waves of the exhaust flow into the sub-cavities in the annular cavity, the radially outer sheet including additional holes configured for transmitting the pressure waves into a downstream-most one of the sub-cavities and for flowing the exhaust flow into the downstream-most one of the sub-cavities.

An aircraft engine, comprising:

• a combustor section configured for combusting a mixture of fuel and air to produce an exhaust flow;
• and
• an exhaust section including an exhaust case extending along a central longitudinal axis between an exhaust inlet receiving the exhaust flow from the combustor section and an exhaust outlet exhausting the exhaust flow, the exhaust section further including an annular body disposed therein and exposed to the exhaust flow, the annular body having a radially outer sheet, a radially inner sheet, an annular cavity defined between the radially outer sheet and the radially inner sheet, one or more plates disposed in the annular body and subdividing the annular cavity into sub-cavities, one or more holes disposed through the radially outer sheet, the one or more holes configured for transmitting acoustic pressure waves of the exhaust flow into the sub-cavities in the annular cavity, the radially outer sheet including additional holes configured for transmitting the pressure waves into a downstream-most one of the sub-cavities and for flowing the exhaust flow into the downstream-most one of the sub-cavities.