ABSTRACT
Introduction .......................................................................................... 130 Overview on special aspects of aircraft noise calculations ..................... 131
Specic properties of aircraft noise calculations ................................ 131 Large areas, no houses .................................................................. 131 Distinct aircraft types and their sound emission ............................ 132 What is considered to be aircraft noise? ........................................ 132 Relevant distances for accurate noise calculations ........................ 133 “Air to ground” sound propagation .............................................. 133 The effect of wind and of temperature gradients ........................... 133 Accounting for topography........................................................... 134
Noise calculation of a single aircraft movement for a single receiver point .................................................................................... 134
Flight path information (position, thrust, speed) ........................... 135 Aircraft sound database ................................................................ 135
The calculation of noise contours ..................................................... 136 Model features, quality requirements, and calculation times ............. 137 Noise metrics .................................................................................... 137 Annoyance ........................................................................................ 138
The scenario .......................................................................................... 138 Aircraft identication ........................................................................ 139 Reducing the number of aircraft types in a noise calculation ............ 140 Modelling of track dispersion ........................................................... 140 Altitude proles ................................................................................ 141 Speed proles .................................................................................... 141 Thrust proles or equivalent indications ........................................... 141
Number of movements .......................................................................... 142 The acoustic kernels (noise calculation programs) ................................. 142
Characterisation of actual programs ................................................. 143 DOC.29 (2005) ............................................................................ 143 INM 7 .......................................................................................... 144
INTRODUCTION
An aircraft noise calculation is considerably more complex than using a program with a specic name. Certainly, the concepts of acoustic models remain important. But there is a large amount of preprocessing and postprocessing to be handled very similarly with any noise calculation program. The fact that a result can be only as good as the input data leads to the importance of the input data preprocessing. Decisions made by the user during preprocessing can easily have a greater impact on the uncertainty of the results than the acoustic model used. Therefore, this chapter on aircraft noise is not a technical manual on how to compute noise with a specic program, but it stresses common features and constraints of all aircraft noise calculation programs.
