Noise Reduction in Helicopter Cabins Using Microperforated Panel Composite Sound Absorption Structures

The high level of noise in helicopter cabins considerably compromises the comfort and safety of the pilot and passengers. To verify the feasibility and effectiveness of microperforated panel composite sound absorption structures for noise suppression in helicopter cabins, simulation and experimental studies were conducted on a model of a light helicopter cabin. First, three microperforated composite sound absorption structures for the helicopter cabin wall panel were designed. Then, a finite element model of the main gear/body acoustic vibration coupling was established to obtain the target frequencies of the microperforated composite sound absorption structures; the acoustic effect was verified via simulation. Finally, a model helicopter cabin equipped with the three microperforated composite sound absorption structures was built, and a cabin noise test was performed. The test results showed that the combined microperforated panel acoustic structure and microperforated panel-porous material composite structure realized an overall cabin sound pressure level attenuation of 8-10 dB, on average, in a wide frequency range of 500-2000 Hz, with an amplitude of more than 20 dB. The microperforated panel-acoustic supermaterial composite structure achieved low-frequency sound absorption in the frequency range of 300-450 Hz. The sound absorption effect reached 50%, and it also exhibited good noise reduction effects in the middle- and high-frequency bands.