Abstract: The acoustic emission from an aircraft during the flight is a dynamic process. The emitting acoustic power and received mean square acoustic pressure are the function of time. The paper deals with this problem as a quasi-steady one. The whole process is resolved into several elementary procedures,for example ,the flight trajectory,the geometric relation between the noise sources and observers,the noise source characteristics,the air propagation and ground effect. Two calculation examples are given in the paper,one for a long-range passenger with high bypass-ratio turbofan engine,another for a 3-leaved propeller. The composition of aircraft noise,and its time record,frequency spectrum and directivity can be clearly described by these curves. It may be useful for the designer to perform the acoustic design of his aircraft layout.

Key words: acoustic emission, mean acoustic pressure, noise source