A REVIEW OF ACOUSTIC SPACE FILLING CURVE METAMATERIALS FOR JET ENGINE INLETS

Aircraft are notorious for their large sound profile, yet noise is one of the most significant limiting factors for aviation growth. In 2011 the World Health Organisation identified environmental noise as the second largest environmental health risk in Western Europe [1]. Prolonged exposure to unacceptable noise levels (≥55 dB Lden (day evening-night level)) is linked to conditions including tinnitus, hypertension, coronary heart disease and myocardial infarctions [2]. Factor such as these have led organisations like the Advisory Council for Aircraft Research and Innovation in Europe (ACARE) to target a reduction in perceived noise by 50% for new aircraft entering into service in 2020 relative to the year-2000 [3]. Moreover, airport operations are often restricted at night, due to factors such as noise therefore noise control offers a potential increased capacity....