5. Propeller acoustics

5.1 Noise. Notions

One of the disadvantages airlines have identified with propeller-driven regional jets is that they are noisier than jet-powered aircraft. Improving acoustic comfort is therefore a prime objective if we are to take full advantage of the benefits of this type of propulsion in this speed range (propulsive efficiency, operating cost, etc.). Noise is the sensory manifestation of a temporal variation in fluid pressure at the level of the human ear. The sensitivity range of the human ear extends from 20 Hz to 20 kHz, and varies according to frequency. The unit of evaluation of this pressure is the decibel (dB) in comparison with the reference pressure,...