Development and Verification of Acoustic Metamaterial Liner for Noise Suppression in Slat

Low-noise design is a crucial technology in the design of civil aircraft. Lift devices are among the primary noise sources during commercial aircraft takeoff and approach, with slat noise often dominating. Due to spatial constraints, traditional porous and honeycomb materials are unable to reduce low-frequency noise effectively. Therefore, based on the subwavelength-scale characteristics of acoustic metamaterials, we have designed compact metaliners for low- to midfrequency noise suppression. The metaliners are placed at the leading edge (LE) of the main wing (meta-LE) and on the inner side of the slat (metaslat). The meta-LE and metaslat exhibit wideband sound absorption capacity in the frequency ranges of 600–1600 Hz and 1500–4000 Hz. Experiments are conducted in the FL52 low-speed wind tunnel. The results indicate that at a freestream velocity of 68 m/s and an angle of attack (AOA) of 12 deg, the meta-LE achieves an average noise reduction of 3.1 dB in the designed frequency across 17 far-field microphones. The metaslat demonstrates an average noise reduction of 1.1 dB in the designed frequency range. Additionally, at an AOA of 16 deg, two tones emerge for the baseline, and the noise from installing the meta-LE and metaslat is reduced by 5.6 and 3.1 dB, respectively, at far-field microphones.