Aircraft Noise Control: Better Acoustic Materials or Better Propulsion Technologies?

Noise is produced by the vibration and disturbance of the fluid, and the greater the amplitudes of vibration, the more noise will be made. Thus, the higher the Mach number of an aircraft in flight, the greater the tendency for mechanical vibration to increase with engine speed. Higher exhaust speeds also contribute to jet noise. In general, lower flight Mach numbers reduce aerodynamic noise but, on the other hand, limit flight speed. Noise pollution is harmful to human physical and mental health, and how to maintain a good flight speed while reducing noise has always been an important issue in aerospace engineering.

One way to tackle this issue is to create new acoustic control materials or structures that can absorb sound or reduce noise. Another strategy is to nip vibration in the bud, meaning to identify the causes of vibration and choose vibration-free/micro-vibration designs. Currently, it is known that with technological advancements, the noise level of electric scooters (approximately 60–75 dB(A)) is lower than that of gasoline motorcycles (80–100 dB(A)) at high speeds. The reason is the configuration of electric power. Although electric scooters are not as fast as gasoline motorcycles, their environmental friendliness and sufficiency for personal use are enough to replace the configuration of gasoline power.

While battery-electric propulsion systems currently does not provide enough power to independently drive a large aircraft, this still means that changing the source of energy will bring about a completely new revolution in future transportation, propulsion engineering, and even industry. This will be a path that can reduce noise pollution and even lead people towards environmental protection and sustainable resources.

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