1. Introduction

1.1 Acoustic comfort and the environment

As with all means of transport, there are two aspects to acoustics in aeronautics.

• Internal noise

  It contributes to crew fatigue and reduces passenger comfort. It is mainly due to the transmission of propulsion noise through the fuselage walls. It is therefore primarily a vibro-acoustic problem, not addressed here.

  Let's just say that progress has been made through better modeling of physical phenomena, optimization of passive absorbers in the fuselage (effective at medium and high frequencies) and active vibration or acoustic controls (effective at low frequencies).