Definition
Sound-absorbing panels installed inside the inlet ducts and exhaust sections of turbofan and turbojet engines. They are typically made of perforated face sheets bonded to a honeycomb core and a solid backing, forming small cavities that trap and dissipate sound energy from the engine.
Plain English
Special panels lining the inside of jet engine air passages that soak up engine noise so less of it escapes to the outside.
Context Anchor
Seen in turbine engine and maintenance discussions, especially during inspections of engine inlets, fan ducts, exhaust areas, and noise-control equipment.
Derivation
Acoustical comes from the Greek 'akoustikos,' meaning 'relating to hearing.' A liner is something that lines, or covers, the inside of a structure. Together: an inner surface that handles sound.
Why Pilots Care
Lower noise output allows operations at noise-sensitive airports and meets regulatory requirements.
Analogy
Similar to the foam panels on the walls of a recording studio, which absorb sound instead of letting it bounce around.
Intuition Check
Do not think of these as simple protective coverings only. In this term, the main purpose of the liner is to absorb and reduce sound.
Example Sentence 1
During the engine inspection, the mechanic checked the acoustical liners in the inlet duct for cracks and delamination.
Example Sentence 2
During preflight, pilots may note acoustical liner inspections as part of engine checks in the logbook.